(a) 25 m (b) 13 m (c) 18 m (d) 17 m Sol.11) (c) Let AB be the given that tree of height h m, which is broken at D which is 12 m away from its base and the height of remaining part,

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Class 7th Mathematics Exemplar Answers Chapter 6 Triangles

Exercise (c) In Examples 1 to 5, there are four options, out of which only one is correct. Write

the correct one.

Q.1) The sides of a triangle have lengths (in cm) 10, 6.5 and a, where 𝑎 is a whole number. The minimum value that a can take is (a) 6 (b) 5 (c) 3 (d) 4

Sol.1) (d) As we know, sum of any two sides in a triangle is always greater than the third side. So, only 4 is the minimum value that satisfies as a side in triangle.

{10 < 6.5 + 46.5 < 10 + 44 < 10 + 6.5

}

Q.2) 𝛥𝐷𝐸𝐹 of following figure is a right angled triangle with ∠𝐸 = 90°. What type of angles are ∠𝐷 and ∠𝐹 (a) They are equal angles (b) They form a pair of adjacent angles

Sol.2) (c) Since, ∠𝐷 and ∠𝐹 are complementary angles. In 𝛥𝐷𝐸𝐹,

∠𝐷 + ∠𝐸 + ∠𝐹 = 180° ∠𝐷 + 90° + ∠𝐹 = 180° ∠𝐷 + ∠𝐹 = 180° − 90° ∠𝐷 + ∠𝐹 = 90°

Q.3) In the given figure, PQ = PS. The value of 𝑥 is

(a) 35° (b) 45° (c) 55° (d) 70°

Sol.3) b) In 𝛥𝑃𝑄𝑆,

110° + ∠1 = 180° ∠1 = 180° − 110° ∠1 = 70° Also, ∠1 = ∠2 = 70° The measure of any exterior angle of a triangle is equal to the sum of the measures of its two interior opposite angles.

∠2 = 𝑥 + 25° 70° = 𝑥 + 25° 𝑥 = 70° − 25° 𝑥 = 45°

Q.4) In a right angled triangle, the angles other than the right angle are

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(a) obtuse (b) right (c) acute (d) straight

Sol.4) In right angled 𝛥𝐴𝐵𝐶,

∠𝐵 = 90°

∠𝐴 + ∠𝐵 + ∠𝐶 = 180° ∠𝐴 + 90° + ∠𝐶 = 180° ∠𝐴 + ∠𝐶 = 180° − 90° = 90° Hence, in a right angled triangle, the angles other than the right angle are acute.

Q.5) In an isosceles triangle, one angle is 70°. The other two angles are of (i) 55° and 55° (ii) 70° and 40° (iii) any measure In the given option(s) which of the above statement(s) are true? (a) (i) only (b) (ii) only (c) (iii) only (d) (i) and (ii)

Sol.5) d) The sum of the interior angles of a triangle is 180.

i) According to the question,

70° + 55° + 55° = 180° ii) A/c,

70° + 70° + 40° = 180° iii) Not possible, because two angles must be equal in an isosceles triangle.

Q.6) In a triangle, one angle is of 90°. Then, (i) the other two angles are of 45° each. (ii) in remaining two angles, one angle is 90° and other is 45°. (iii) remaining two angles are complementary. In the given option(s) which is true? (a) (i) only (b) (ii) only (c) (iii) only (d) (i) and (ii)

Sol.6) (c) In a right angled 𝛥𝐴𝐵𝐶,

∠𝐵 = 90 Now, ∠𝐴 + ∠𝐵 + ∠𝐶 = 180°

∠𝐴 + 90° + ∠𝐶 = 180° ∠𝐴 + ∠𝐶 = 180° − 90° = 90° Hence, remaining two angles are complementary.

Q.7) Lengths of sides of a triangle are 3 cm, 4 cm and 5 cm. The triangle is (a) obtuse angled triangle



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(b) acute angled triangle (c) right angled triangle (d) an isosceles right triangle

Sol.7) (c) Since, these sides satisfy the Pythagoras theorem, therefore it is right angled triangle. Lengths of the sides of a triangle are 3 cm, 4 cm and 5 cm. According to Pythagoras theorem, 32 + 42 = 52 9 + 16 = 25 25 = 25 Note: The area of the square built upon the hypotenuse of a right angled triangle is equal to the sum of the areas of the squares upon the remaining sides is known as Pythagoras theorem.

Q.8) In the given figure, PB = PD. The value of 𝑥 is

(a) 85° (b) 90° (c) 25° (d) 35°

Sol.8) (c) In a right angled 𝛥𝑃𝐵𝐷,

∠1 + 120° = 180° Now, ∠1 = 180° − 120° = 60°

∠1 + ∠2 = 60° Also, ∠2 + ∠3 = 180°

60° + ∠3 = 180° ∠3 = 180° − 60° ∠3 = 120° In 𝛥𝑃𝐷𝐶, 35° + ∠3 + 𝑥 = 180°

35° + 120° + 𝑥 = 180° 𝑥 = 180° − 155° = 25° 𝑥 = 25°

Q.9) In 𝛥𝑃𝑄𝑅, (a) PQ – QR > PR (b) PQ +QR< PR (c) PQ-QR< PR (d) PQ +<PR

Sol.9) (c) As we know, sum of the lengths of any two sides of a triangle is always greater than the length of the third side. In 𝛥𝑃𝑄𝑅, 𝑃𝑅 + 𝑄𝑅 > 𝑃𝑄 𝑃𝑅 > 𝑃𝑄 − 𝑄𝑅 𝑃𝑄 − 𝑄𝑅 < 𝑃𝑅

Q.10) In 𝛥𝐴𝐵𝐶, (a) AB+BC> AC (b) AB + BC< AC (c) AB+AC < BC (d) AC + BC< AB

Sol.10) (a) As we know, sum of any two sides in a triangle is always greater than the third side. In 𝛥 𝐴𝐵𝐶,



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𝐴𝐵 + 𝐵𝐶 > 𝐴𝐶 Q.11) The top of a broken tree touches the ground at a distance of 12 m from its base. If the

tree is broken at a height of 5 m from the ground, then the actual height of the tree is (a) 25 m (b) 13 m (c) 18 m (d) 17 m

Sol.11) (c) Let AB be the given that tree of height h m, which is broken at D which is 12 m away from its base and the height of remaining part, i.e. CS is 5 m. In the given figure, BC represents the unbroken part of the tree. Point C represents the point where the tree broke and CA represents the broken part of the tree. Triangle ABC, thus formed, is right-angled at B. Applying Pythagoras theorem in ΔABC, 𝐴𝐶2 = 𝐵𝐶2 + 𝐴𝐵2 𝐴𝐶2 = (5 𝑚)2 + (12 𝑚)2 𝐴𝐶2 = 25 𝑚2 + 144 𝑚2 = 169 𝑚2 𝐴𝐶 = 13 𝑚 Thus, original height of the tree = 𝐴𝐶 + 𝐶𝐵 = 13 𝑚 + 5 𝑚 = 18𝑚

Q.12) The triangle ABC formed by 𝐴𝐵 = 5 𝑐𝑚, 𝐵𝐶 = 8 𝑐𝑚, 𝐴𝐶 = 4 𝑐𝑚 is (a) an isosceles triangle only (b) a scalene triangle only (c) an isosceles right triangle (d) scalene as well as a right triangle

Sol.12) (b) (i) It’s not isosceles triangle as all the sides are of different measure. (ii) It’s not right triangle, since it does not follow Pythagoras theorem.

42 + 52 = 82 16 + 25 = 64 41 ≠ 64 (not satisfied) Hence, it is a scalene triangle as all the sides are of different measure.

Q.13) Two trees 7 m and 4 m high stand upright on a ground. If their bases (roots) are 4 m apart, then the distance between their tops is (a) 3 m (b) 5 m (c) 4 m (d) 11 m

Sol.13) (b) Let 𝐵𝐸 be the smaller tree and AD be the bigger tree. Now, we have to find AB (i.e. the distance between their tops). Given: Two trees 𝐸𝐷 = 𝐵𝐶 = 4𝑚 and 𝐵𝐸 = 𝐶𝐷 = 4𝑚 In 𝛥𝐴𝐵𝐶, 𝐵𝐶 = 4𝑚



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And 𝐴𝐶 = 𝐴𝐷 − 𝐶𝐷 = (7 − 4)𝑚 = 3𝑚 In right angled 𝛥𝐴𝐵𝐶, By Pythagoras theorem, 𝐴𝐵2 = 𝐴𝐶2 + 𝐵𝐶2 = 42 + 32 = 16 + 9 𝐴𝐵2 = 252 𝐴𝐵 = 5𝑚 ∴ Distance between the tops of two trees = 5 𝑚.

Q.14) If in an isosceles triangle, each of the base angle is 40°, then the triangle is (a) right angled triangle (b) acute angled triangle (c) obtuse angled triangle (d) isosceles right angled triangle

Sol.14) (c) As we know, the sum of the interior angles of a triangle is 180°. In 𝛥𝐴𝐵𝐶,

∠𝐴 + ∠𝐵 + ∠𝐶 = 180° ∠𝐴 + 40° + 40° = 180° ∠𝐴 = 180° − 80° ∠𝐴 = 100° Therefore, it is an obtuse angled triangle. Since, it has one angle which is greater than

90°.

Q.15) If two angles of a triangle are 60° each, then the triangle is (a) isosceles but not equilateral (b) scalene (c) equilateral (d) right angled

Sol.15) In 𝛥𝐴𝐵𝐶,

∠𝐴 + ∠𝐵 + ∠𝐶 = 180° ∠𝐴 + 60° + 60° = 180° ∠𝐴 = 180° − 120° ∠𝐴 = 60° Since, all the angles are of 60. So, it is an equilateral triangle.

Q.16) The perimeter of the rectangle whose length is 60 cm and a diagonal is 61 cm is (a) 120 cm (b) 122 cm (c) 71 cm (d) 142 cm

Sol.16) d) 𝐴𝐶2 = 𝐴𝐵2 + 𝐵𝐶2 𝐵𝐶2 = 𝐴𝐶2 − 𝐴𝐵2 = (61)2 − (60)2 = 3721 − 3600 𝐵𝐶2 = 121

𝐵𝐶 = √121 = 11 So, perimeter of rectangle = 2(𝑙 + 𝑏) = 2(60 + 11) = 2(71) = 142𝑐𝑚

Q.17) In ∆𝑃𝑄𝑅, if PQ = QR and ∠𝑄 = 100°, then ∠R is equal to (a) 40° (b) 80° (c) 120° (d) 50°

Sol.17) a) In ∆𝑃𝑄𝑅, 𝑃𝑄 = 𝑄𝑅



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Let ∠𝑃 = ∠𝑅 = 𝑥

∠𝑃 + ∠𝑄 + ∠𝑅 = 180° 𝑥 + 100 + 𝑥 = 180° 2𝑥 + 100 = 180° 2𝑥 = 80° 𝑥 = 40° Hence, ∠𝑃 = ∠𝑅 = 40°

Q.18) Which of the following statements is not correct? (a) The sum of any two sides of a triangle is greater than the third side (b) A triangle can have all its angles acute (c) A right angled triangle cannot be equilateral (d) Difference of any two sides of a triangle is greater than the third side

Sol.18) (d) The difference of the length of any two sides of a triangle is always smaller than the length of the third side.

Q.19) In the given figure, 𝐵𝐶 = 𝐶𝐴 and ∠𝐴 = 40°. Then, ∠𝐴𝐶𝐷 is equal to

(a) 40° (b) 80° (c) 120° (d) 60°

Sol.19) b) Given, 𝐵𝐶 = 𝐶𝐴

∠𝐵 = ∠𝐴 = 40° The measure of any exterior angle of a triangle is equal to the sum of the measure of its two interior opposite angles.

So, ∠𝐴𝐶𝐷 = ∠𝐴 + ∠𝐵 = 40° + 40°

∠𝐴𝐶𝐷 = 80° Q.20) The lengths of two sides of a triangle are 7 cm and 9 cm. The length of the third side

may lie between (a) 1 cm and 10 cm (b) 2 cm and 8 cm (c) 2 cm and 16 cm (d) 1 cm and 16 cm

Sol.20) (c) The third side must be greater than the difference between two sides and less than the sum of two sides. Sum of two sides = 7 + 9 = 16 𝑐𝑚

Difference of two sides = 9 – 7 = 2 𝑐𝑚 So, length of the third side must lie between 2 cm and 16 cm.

Q.21) From Fig., the value of 𝑥 is

(a) 75° (b) 90° (c) 120° (d) 60°

Sol.21) c) In 𝛥𝐴𝐵𝐶,

∠𝐶𝐴𝐵 + ∠𝐴𝐵𝐶 + ∠𝐵𝐶𝐴 = 180° 25 + 35 + ∠𝐵𝐶𝐴 = 180°



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∠𝐵𝐶𝐴 = 180° − 60° = 120° ∠𝐵𝐶𝐴 = 120° ALSO, ∠𝐵𝐶𝐴 is an exterior angle, ∠𝐵𝐶𝐴 = ∠𝐷 + 𝑦 𝑦 = ∠𝐵𝐶𝐴 − ∠𝐷 = 120° − 60° 𝑦 = 60° Now, ∠𝑥 and ∠𝑦 form a linear pair

𝑥 + 𝑦 = 180° 𝑥 + 60° = 180° 𝑥 = 180° − 60° = 120°

Q.22) In Fig., the value of ∠𝐴 + ∠ 𝐵 + ∠𝐶 + ∠𝐷 + ∠𝐸 + ∠𝐹 is

(a) 190° (b) 540° (c) 360° (d) 180°

Sol.22) As we know, sum of all the interior angles of a triangle is 180°

In ∆𝐴𝐵𝐶, ∠𝐴 + ∠𝐵 + ∠𝐶 = 180°

In ∆𝐷𝐸𝐹, ∠𝐷 + ∠𝐸 + ∠𝐹 = 180° On adding eq. (i) and (ii), we get

∠𝐴 + ∠𝐵 + ∠𝐶 + ∠𝐷 + ∠𝐸 + ∠𝐹 = 180° + 180° = 360° Q.23) In Fig., 𝑃𝑄 = 𝑃𝑅, 𝑅𝑆 = 𝑅𝑄 and 𝑆𝑇 || 𝑄𝑅. If the exterior angle 𝑅𝑃𝑈 is 140°, then

the measure of angle TSR is

(a) 55° (b) 40° (c) 50° (d) 45°

Sol.23) ∠1 + ∠𝑃 = 180° ∠1 + 140° = 180° ∠1 = 180° − 140° = 40° Since, 𝑃𝑄 = 𝑃𝑅 ∠𝑄 = ∠𝑅 = 𝑥 In ∆𝑃𝑄𝑅, ∠𝑃 + ∠𝑄 + ∠𝑅 = 180°

40° + 𝑥 + 𝑥 = 180° 2𝑥 = 180° − 40°

𝑥 =140°

2= 70°

So, ∠𝑄 + ∠𝑅 = 70° Given that, 𝑅𝑆 = 𝑅𝑄

∠2 = ∠3 = 70° In ∆𝑆𝑄𝑅, ∠2 + ∠3 + ∠4 = 180°

70° + 70° + ∠4 = 180° ∠4 = 180° − 140° = 40°



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Also, 𝑆𝑇 || 𝑄𝑅

Now, ∠4 = ∠6 = 40° [alternate interior angles]

∠𝑇𝑆𝑅 = 40° Q.24) In Fig., ∠𝐵𝐴𝐶 = 90°, AD BC and ∠𝐵𝐴𝐷 = 50°, then ∠𝐴𝐶𝐷 is

(a) 50° (b) 40° (c) 70° (d) 60°

Sol.24) a) Given, ∠𝐵𝐴𝐶 = 90°, AD BC and ∠𝐵𝐴𝐷 = 50° in ∆𝐴𝐵𝐷, ∠𝐴𝐵𝐷 + ∠𝐷𝐴𝐵 + ∠𝐴𝐷𝐵 = 180 ∠𝐴𝐵𝐷 + 50 + 90 = 180 ∠𝐴𝐵𝐷 + 40 = 180 ∠𝐴𝐵𝐷 = 180 − 40 = 40 Now, in ∆𝐴𝐵𝐶, ∠𝐴 + ∠𝐵 + ∠𝐶 = 180 90 + 40 + ∠𝐶 = 180 ∠𝐶 = 180 − 130 ∠𝐶 = 50 ∠𝐴𝐶𝐷 = 50

Q.25) If one angle of a triangle is equal to the sum of the other two angles, the triangle is (a) obtuse (b) acute (c) right (d) equilateral

Sol.25) Let A, B and C be the angles of the triangle. Then, one angle of a triangle is equal to the sum of the other two angles. i.e., ∠𝐴 = ∠𝐵 + ∠𝐶 ∠𝐴 + ∠𝐵 + ∠𝐶 = 180° ∠𝐴 + ∠𝐴 = 180° 2∠𝐴 = 180°

∠𝐴 =180°

2

∠𝐴 = 90° Hence, the triangle is right angled.

Q.26) If the exterior angle of a triangle is 130° and its interior opposite angles are equal, then measure of each interior opposite angle is (a) 55° (b) 65° (c) 50° (d) 60°

Sol.26) (b) As we know, the measure of any exterior angle is equal to the sum of two opposite interior angles. Let the interior angle be 𝑥. Given that, interior opposite angles are equal. 130° = 𝑥 + 𝑥 130° = 2𝑥

𝑥 =130°

2= 65°

Hence, the interior angle is 65°

Q.27) If one of the angles of a triangle is 110°, then the angle between the bisectors of the other two angles is (a) 70° (b) 110° (c) 35° (d) 145°



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Sol.27) (d) In ∆𝐴𝐵𝐶, ∠𝐴 = 110° We know that, ∠𝐴 + ∠𝐵 + ∠𝐶 = 180° ∠𝐵 + ∠𝐶 = 180° − ∠𝐴 ∠𝐵 + ∠𝐶 = 180° − 110° ∠𝐵 + ∠𝐶 = 70°

1

2 ∠𝐵 +

1

2 ∠𝐶 =

70°

2= 45°

1

2(∠𝐵 + ∠𝐶) = 35°

Now, in ∆𝐵𝑂𝐶, ∠𝐵𝑂𝐶 + ∠𝑂𝐵𝐶 + ∠𝑂𝐶𝐵 = 180°

∠𝐵𝑂𝐶 +1

2 (∠𝐵 + ∠𝐶) = 180°

∠𝐵𝑂𝐶 + 35° = 180° ∠𝐵𝑂𝐶 = 180° − 35° ∠𝐵𝑂𝐶 = 145°

Q.28) In ∠𝐴𝐵𝐶, AD is the bisector of 𝐴 meeting BC at D, CFAB and E is the mid-point of AC. Then median of the triangle is (a) AD (b) BE (c) FC (d) DE

Sol.28) (b) As we know, median of a triangle bisects the opposite sides.

Hence, the median is BE as 𝐴𝐸 = 𝐸𝐶

Q.29) In 𝛥𝑃𝑄𝑅, if ∠𝑃 = 60° and ∠𝑄 = 40°, then the exterior angle formed by producing QR is equal to (a) 60° (b) 120° (c) 100° (d) 80°

Sol.29) c) As we know, the measure of exterior angle is equal to the sum of opposite two interior angles.

In ∆𝑃𝑄𝑅, ∠𝑥 is the exterior angle So, ∠𝑥 = ∠𝑃 + ∠𝑄 = 60° + 40° = 100°

Q.30) Which of the following triplets cannot be the angles of a triangle? (a) 67°, 51°, 62° (b) 70°, 83°, 27°

(c) 90°, 70°, 20° (d) 40°, 132°, 18°

Sol.30) (d) We know that, the sum of interior angles of a triangle is 180. Now, we will verify the given triplets: (a) 67° + 51° + 62° = 180° (b) 70° + 83° + 27° = 180°



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(c) 90° + 70° + 20° = 180° (d) 40° + 132° + 18° = 190° Clearly, triplets in option (d) cannot be the angles of a triangle.

Q.31) Which of the following can be the length of the third side of a triangle whose two sides measure 18 cm and 14 cm? (a) 4 cm (b) 3 cm (c) 5 cm (d) 32 m

Sol.31) (c) As we know, sum of any two sides of a triangle is always greater than the third side. Hence, option (c) satisfies the given condition. Verification 18 + 14 > 5 18 + 5 > 14 5 + 14 > 18

Q.32) How many altitudes does a triangle have? (a) 1 (b) 3 (c) 6 (d) 9

Sol.32) (b) A triangle has 3 altitudes

Q.33) If we join a vertex to a point on opposite side which divides that side in the ratio 1:1, then what is the special name of that line segment? (a) Median (b) Angle bisector (c) Altitude (d) Hypotenuse

Sol.33) (a) Consider 𝛥𝐴𝐵𝐶 in which AD divides BC in the ratio 1:1. Now, 𝐵𝐷: 𝐷𝐶 = 1: 1 𝐵𝐷

𝐷𝐶=

1

1

𝐵𝐷 = 𝐷𝐶

Since, AD divides BC into two equal parts. Hence, AD is the median.

Q.34) The measures of ∠𝑥 and ∠𝑦 in the given figure are respectively

(a) 30°, 60° (b) 40°, 40° (c) 70°, 70° (d) 70°, 60°

Sol.34) (d) As we know, Measure of exterior angle = sum of the opposite interior angles ∠𝑅 = ∠𝑃 + ∠𝑄 120° = 𝑥 + 50 𝑥 = 120° − 50° = 70° Now, the sum of the interior angles

Q.35) If two sides of a triangle are 6 cm and 10 cm, then the length of the third side can be (a) 3 cm (b) 4 cm (c) 2 cm (d) 6 cm

Sol.35) (d) As we know, sum of any two sides of a triangle is always greater than the third side. So, option (d) satisfy this rule.



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Verification 6 + 6 > 10 6 + 10 > 6 10 + 6 > 6

Q.36) In a right angled 𝛥𝐴𝐵𝐶, if ∠𝐵 = 90°, 𝐵𝐶 = 3 𝑐𝑚 and AC = 5 cm, then the length of side AB is (a) 3 cm (b) 4 cm (c) 5 cm (d) 6 cm

Sol.36) (b) Since, 𝛥 𝐴𝐵𝐶 is a right angled triangle. In right angled ∆𝐴𝐵𝐶, 𝐴𝐶2 = 𝐴𝐵2 + 𝐵𝐶2 52 = 𝐴𝐵2 + 32 𝐴𝐵2 = 25 − 9 𝐴𝐵2 = 16 𝐴𝐵 = 4𝑐𝑚

Q.37) In a right angled 𝛥𝐴𝐵𝐶, if ∠𝐵 = 90°, then which of the following is true? (a) 𝐴𝑆2 = 𝐵𝐶2 + 𝐴𝐶2 (b) 𝐴𝐶2 = 𝐴𝐵2 + 𝐵𝐶2 (c) AB = BC + AC (d) AC = AB + BC

Sol.37) b) According to Pythagoras theorem,

𝐴𝐶2 = 𝐴𝐵2 + 𝐵𝐶2

Q.38) Which of the following figures will have it’s altitude outside the triangle?

Sol.38) (d) As we know, the perpendicular line segment from a vertex of a triangle to its

opposite side is called an altitude of the triangle.

Q.39) In the given figure, if 𝐴𝐵 || 𝐶𝐷, then.

(a) ∠ 2 = ∠3 (b) ∠1 = ∠4 (c) ∠4 = ∠1 + ∠2 (d) ∠1 + ∠2 = ∠3 + ∠4

Sol.39) (d) Given, 𝐴𝐵 || 𝐶𝐷 and AC is the transversal. So, ∠1 = ∠3 Also, in ∆𝐴𝐵𝐶, ∠3 + ∠4 = ∠1 + ∠2

Q.40) In 𝛥𝐴𝐵𝐶, ∠𝐴 = 100°, AD bisects ∠𝐴 and 𝐴𝐷 ⊥ 𝐵𝐶. Then, ∠𝐵 is equal to (a) 80° (b) 20° (c) 40° (d) 30°

Sol.40) (c) Given, ∠𝐵𝐴𝐷 = ∠𝐷𝐴𝐶 = 50° ∠𝐵𝐷𝐴 = ∠𝐴𝐷𝐶 = 90° Now, in ∆𝐴𝐵𝐷, ∠𝐴𝐵𝐷 + ∠𝐵𝐴𝐷 + ∠𝐵𝐷𝐴 = 180°



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∠𝐴𝐵𝐷 + 50° + 90° = 180° ∠𝐴𝐵𝐷 + 140° = 180° ∠𝐴𝐵𝐷 = 180° − 140° = 40°

Q.41) In 𝛥𝐴𝐵𝐶, ∠𝐴 = 50°, ∠𝐵 = 70° and bisector of ∠𝐶 meets AB in D as shown in the given figure. Measure of ∠𝐴𝐷𝐶 is

(a) 50° (b) 100° (c) 30° (d) 70°

Sol.41) (b) In ∆𝐴𝐷𝐶, ∠𝐴𝐷𝐶 + ∠𝐷𝐴𝐶 + ∠𝐴𝐶𝐷 = 180° ∠𝐴𝐷𝐶 + 50° + ∠𝐴𝐶𝐷 = 180° ∠𝐴𝐶𝐷 = 130° − ∠𝐴𝐷𝐶 In ∆𝐷𝐵𝐶, ∠𝐴𝐷𝐶 = ∠𝐷𝐵𝐶 + ∠𝐵𝐶𝐷 ∠𝐴𝐷𝐶 = 70° + ∠𝐴𝐶𝐷 ∠𝐴𝐷𝐶 = 70° + 130° − ∠𝐴𝐷𝐶 ∠𝐴𝐷𝐶 = 200° − ∠𝐴𝐷𝐶 2∠𝐴𝐷𝐶 = 200°

∠𝐴𝐷𝐶 =200°

2= 100°

Q.42) If for ∆𝐴𝐵𝐶 and ∆𝐷𝐸𝐹, the correspondence 𝐶𝐴𝐵 ↔ 𝐸𝐷𝐹 gives a congruence, then which of the following is not true? (a) 𝐴𝐶 = 𝐷𝐸 (b) AB = EF (c) ∠𝐴 = ∠𝐷 (d) ∠𝐶 = ∠𝐸

Sol.42) (b) Two figures are said to be congruent, if the trace copy of figure 1 fits exactly on that of fig. 2

Now, if ∆𝐴𝐵𝐶 and ∆𝐷𝐸𝐹 are congruent, then 𝐴𝐵 = 𝐷𝐹, 𝐵𝐶 = 𝐸𝐹 𝐴𝐶 = 𝐷𝐸, ∠𝐴 = ∠𝐷 ∠𝐵 = ∠𝐹, ∠𝐶 = ∠𝐸 Hence, option (b) is not true.

Q.43) In the given figure, M is the mid-point of both AC and BD. Then, (a) ∠1 = ∠2 (b) ∠1 = ∠4 (c) ∠2 = ∠4 (d) ∠1 = ∠3

Sol.43) (b) In ∆𝐴𝑀𝐵 and ∆𝐶𝑀𝐷, 𝐴𝑀 = 𝐶𝑀 𝐵𝑀 = 𝐷𝑀 ∠𝐴𝑀𝐵 = ∠𝐶𝑀𝐷 By SAS congruence criterion, ∆𝐴𝑀𝐵 ≅ ∆𝐶𝑀𝐷 ∠1 = ∠4 [by CPCT]

Q.44) If D is the mid-point of side BC in 𝛥𝐴𝐵𝐶, where AB = AC, then ∠ADC is



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(a) 60° (b) 45° (c) 120° (d) 90°

Sol.44) (d) In ∆𝐴𝐷𝐵 and ∆𝐴𝐷𝐶, 𝐵𝐷 = 𝐷𝐶 𝐴𝐵 = 𝐴𝐶 𝐴𝐷 = 𝐴𝐷 By SSS congruence criterion, ∆𝐴𝐵𝐷 ≅ ∆𝐴𝐶𝐷 ∠𝐴𝐷𝐵 = ∠𝐴𝐷𝐶 We know that, ∠𝐴𝐷𝐵 + ∠𝐴𝐷𝐶 = 180° 2∠𝐴𝐷𝐶 = 180° ∠𝐴𝐷𝐶 = 90°

Q.45) Two triangles are congruent, if two angles and the side included between them in one of the triangles are equal to the two angles and the side included between them of the other triangle. This is known as the (a) RHS congruence criterion (b) ASA congruence criterion (c) SAS congruence criterion (d) AAA congruence criterion

Sol.45) (b) Under ASA congruence criterion, two triangles are congruent, if two angles and the side included between them in one of the triangles are equal to the two angles and the side included between them of the other triangle.

Q.46) By which congruency criterion, the two triangles in the given figure are congruent?

(a) RHS (b) ASA (c) SSS (d) SAS

Sol.46) (c) In ∆𝑃𝑄𝑅 and ∆𝑃𝑄𝑆, 𝑃𝑅 = 𝑃𝑆 = 𝑎 𝑐𝑚 𝑅𝑄 = 𝑆𝑄 = 𝑏 𝑐𝑚 𝑃𝑄 = 𝑃𝑄 = common line segment By SSS Congruence criterion, ∆𝑃𝑄𝑅 ≅ ∆𝑃𝑄𝑆

Q.47) By which of the following criterion two triangles cannot be proved congruent? (a) AAA (b) SSS (c) SAS (d) ASA

Sol.47) (a) AAA is not a congruency criterion, because if all the three angles of two triangles are equal; this does not imply that both the triangles fit exactly on each other.

Q.48) If 𝛥𝑃𝑄𝑅 is congruent to 𝛥𝑆𝑇𝑈 as shown in the given figure, then what is the length of TU?

(a) 5 cm (b) 6 cm (c) 7 cm (d) cannot be determined



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Sol.48) (b) Given, 𝛥𝑃𝑄𝑅 ≅ 𝛥𝑆𝑇𝑈 𝑃𝑄 = 𝑆𝑇 𝑄𝑅 = 𝑇𝑈 𝑃𝑅 = 𝑆𝑈 Hence, 𝑇𝑈 = 𝑄𝑅 = 6𝑐𝑚

Q.49) If ΔABC and ΔDBC are on the same base BC, AB = DC and AC = DB as shown in the given figure, then which of the following gives a congruence relationship?

(a) ∆𝐴𝐵𝐶 ≅ ∆𝐷𝐵𝐶 (b) ∆𝐴𝐵𝐶 ≅ ∆𝐶𝐵𝐷 (c) ∆𝐴𝐵𝐶 ≅ ∆𝐷𝐶𝐵 (d) ∆𝐴𝐵𝐶 ≅ ∆𝐵𝐶𝐷

Sol.49) (c) Since, 𝐴𝐵 = 𝐷𝐶 𝐴𝐶 = 𝐷𝐵 𝐵𝐶 = 𝐵𝐶 By SSS congruence criterion, ∆𝐴𝐵𝐶 ≅ ∆𝐷𝐶𝐵

Fill in the Blanks In questions 50 to 69, fill in the blanks to make the statements true.

Q.50) The_______triangle always has altitude outside itself.

Sol.50) The obtuse angled triangle always has altitude outside itself.

Q.51) The sum of an exterior angle of a triangle and its adjacent angle is always______.

Sol.51) The sum of an exterior angle of a triangle and its adjacent angle is always, 180°, because they form a linear pair.

Q.52) The longest side of a right angled triangle is called its______.

Sol.52) Hypotenuse is the longest side of a right angled triangle.

Q.53) Median is also called______in an equilateral triangle

Sol.53) Median is also called an altitude in an equilateral triangle.

Q.54) Measures of each of the angles of an equilateral triangle is ______ .

Sol.54) Measures of each of the angles of an equilateral triangle is 60° as all the angles in an equilateral triangle are equal. Let 𝑥 be the angle of equilateral. According to the question, the angle sum property of a triangle 𝑥 + 𝑥 + 𝑥 = 180° 3𝑥 = 180°

𝑥 =180°

3= 60°

Q.55) In an isosceles triangle, two angles are always______.

Sol.55) In an isosceles triangle, two angles are always equal. Since, if two sides are equal, then the angles opposite them are equal.

Q.56) In an isosceles triangle, angles opposite to equal sides are______.

Sol.56) In an isosceles triangle, angles opposite to equal sides are equal. Since, if two angles are equal then the sides opposite to them are also equal.

Q.57) If one angle of a triangle is equal to the sum of other two, then the measure of that



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angle is______.

Sol.57) Let the angles of a triangle be a, band c. It is given that, 𝑎 = 𝑏 + 𝑐 𝑎 + 𝑏 + 𝑐 = 180° 𝑎 + 𝑎 = 180° 2𝑎 = 180°

𝑎 =180°

2= 90°

Hence, the measure of that angle is 90°.

Q.58) Every triangle has atleast______acute angle (s).

Sol.58) Every triangle has atleast two acute angles

Q.59) Two line segments are congruent, if they are of______lengths.

Sol.59) Two line segments are congruent, if they are of equal lengths.

Q.60) Two angles are said to be______, if they have equal measures.

Sol.60) Two angles are said to be congruent, if they have equal measures.

Q.61) Two rectangles are congruent, if they have same______and_____.

Sol.61) Two rectangles are congruent, if they have same length and breadth.

Q.62) Two squares are congruent, if they have same ____.

Sol.62) Two squares are congruent, if they have same side.

Q.63) If 𝛥𝑃𝑄𝑅 and 𝛥𝑋𝑌𝑍 are congruent under the correspondence 𝑄𝑃𝑅 ↔ 𝑋𝑌𝑍, then (i) ∠R =______ (ii) QR =______ (iii) ∠P =______ (iv) QP = ______ (v) ∠Q =______ (vi) RP =______

Sol.63) Given, ∆𝑄𝑃𝑅 ≅ ∆𝑋𝑌𝑍

(i) ∠𝑅 = ∠𝑍 (ii) 𝑄𝑅 = 𝑋𝑍 (iii) ∠𝑃 = ∠𝑌 (iv) QP = XY (v) ∠𝑄 = ∠𝑋 (vi) RP = ZY

Q.64) In the given figure, 𝛥𝑃𝑄𝑅 ≅ 𝛥 ……….. .

Sol.64) In ∆𝑃𝑄𝑅 and ∆𝑋𝑌𝑍

𝑃𝑄 = 𝑋𝑍 = 3.5𝑐𝑚 𝑄𝑅 = 𝑍𝑌 = 5𝑐𝑚 ∠𝑃𝑄𝑅 = ∠𝑋𝑌𝑍 = 45 By SAS congruence criterion, 𝛥𝑃𝑄𝑅 ≅ 𝛥𝑋𝑌𝑍

Q.65) In the given figure, 𝛥𝑃𝑄𝑅 ≅ 𝛥 ……….. 𝛥 ……….. ≅ 𝛥𝑃𝑄𝑅

Sol.65) In ∆𝑃𝑄𝑅 and ∆𝑅𝑆𝑃

𝑄𝑅 = 𝑆𝑃 = 4.1𝑐𝑚



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𝑃𝑅 = 𝑃𝑅 ∠𝑆𝑃𝑅 = ∠𝑄𝑅𝑃 = 45 By SAS congruence criterion, 𝛥𝑃𝑄𝑅 ≅ 𝛥𝑅𝑆𝑃

Q.66) In the given figure, 𝛥 ……….. ≅ 𝛥𝑃𝑄𝑅

Sol.66) In given fig. ∆𝐷𝑅𝑄 and ∆𝑃𝑄𝑅,

𝑄𝑅 = 𝑄𝑅 ∠𝐷𝑅𝑄 = ∠𝑃𝑄𝑅 = 70° ∠𝐷𝑄𝑅 = ∠𝑃𝑅𝑄 = 40° By ASA congruence criterion, ∆𝐷𝑅𝑄 ≅ ∆𝑃𝑄𝑅

Q.67) In the given figure, 𝛥𝐴𝑅𝑂 ≅ 𝛥 ………..

Sol.67) In ∆𝐴𝑅𝑂 and ∆𝑃𝑄𝑂, ∠𝐴𝑂𝑅 = ∠𝑃𝑂𝑄

∠𝐴𝑅𝑂 = ∠𝑃𝑄𝑂 = 55 Now, in ∆𝐴𝑅𝑂 and ∆𝑃𝑄𝑂, ∠𝐴𝑄𝑅 = ∠𝑃𝑂𝑄 𝐴𝑂 = 𝑃𝑂 = 2.5𝑐𝑚 ∠𝑅𝐴𝑄 = ∠𝑄𝑃𝑂 By ASS congruence criterion, ∆𝐴𝑅𝑂 ≅ ∆𝑃𝑄𝑂

Q.68) In the given figure, AB = AD and ∠𝐵𝐴𝐶 = ∠𝐷𝐴𝐶. Then,

(i) 𝐴____ ≅ 𝐴𝐵𝐶 (ii) BC =___ . (iii) ∠𝐵𝐶𝐴 = ______ . (iv) Line segment AC bisects___ and_____ .

Sol.68) i) In ∆𝐴𝐵𝐶 and ∆𝐴𝐷𝐶 𝐴𝐵 = 𝐴𝐷 𝐴𝐶 = 𝐴𝐶 ∠𝐵𝐴𝐶 = ∠𝐷𝐴𝐶 By SAS congruence criterion, ∆𝐴𝐷𝐶 ≅ ∆𝐴𝐵𝐶 ii) BC = DC iii) Also, ∠𝐵𝐶𝐴 = ∠𝐷𝐶𝐴 iv) Line segment AC bisects ∠𝐵𝐴𝐷 and ∠𝐵𝐶𝐷 Since, ∠𝐵𝐴𝐶 = ∠𝐷𝐴𝐶 And ∠𝐵𝐶𝐴 = ∠𝐷𝐶𝐴

Q.69) In the given figure,



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(i) ∠𝑇𝑃𝑄 = ∠______ + ∠______ (ii) ∠𝑈𝑄𝑅 = ∠______ + ∠______ (iii) ∠𝑃𝑅𝑆 = ∠______ + ∠______

Sol.69) Exterior angle property The measure of an exterior angle is equal to the sum of the two opposite interior angles. (i) ∠𝑇𝑃𝑄 = ∠𝑃𝑄𝑅 + ∠𝑃𝑅𝑄 (ii) ∠𝑈𝑄𝑅 = ∠𝑄𝑅𝑃 + ∠𝑄𝑃𝑅 (iii) ∠𝑃𝑅𝑆 = ∠𝑅𝑃𝑄 + ∠𝑅𝑄𝑃

True/False In questions 70 to 106, state whether the statements are True or False.

Q.70) In a triangle, sum of squares of two sides is equal to the square of the third side.

Sol.70) False Only in a right angled triangle, the sum of two shorter sides is equal to the square of the third side.

Q.71) Sum of two sides of a triangle is greater than or equal to the third side

Sol.71) False Sum of two sides of a triangle is greater than the third side

Q.72) The difference between the lengths of any two sides of a triangle is smaller than the length of third side.

Sol.72) True The difference between the lengths of any two sides of a triangle is smaller than the length of third side. e.g., 𝐴𝐵 − 𝐵𝐶 < 𝐴𝐶

Q.73) In 𝛥𝐴𝐵𝐶, 𝐴𝐵 = 3.5 𝑐𝑚, 𝐴𝐶 = 5 𝑐𝑚, 𝐵𝐶 = 6 𝑐𝑚 and in 𝛥𝑃𝑄𝑅, 𝑃𝑅 = 3.5 𝑐𝑚, 𝑃𝑄 = 5 𝑐𝑚, 𝑅𝑄 = 6 𝑐𝑚. Then, 𝛥𝐴𝐵𝐶 ≅ 𝛥𝑃𝑄𝑅.

Sol.73) False In ∆𝐴𝐵𝐶 and ∆𝑃𝑅𝑄,

𝐴𝐵 = 𝑃𝑅 = 3.5𝑐𝑚, 𝐵𝐶 = 𝑅𝑄 = 6𝑐𝑚 and 𝐴𝐶 = 𝑃𝑄 = 5𝑐𝑚 By SSS congruence criterion, ∆𝐴𝐵𝐶 ≅ ∆𝑃𝑅𝑄

Q.74) Sum of any two angles of a triangle is always greater than the third angle.

Sol.74) False It is not necessary that sum of any two angles of a triangle is always greater than the third angle, e.g. Let the angles of a triangle be 20°, 50° and 110°, respectively. Hence, 20° + 50° = 70°, which is less than 110°.

Q.75) The sum of the measures of three angles of a triangle is greater than 180°.

Sol.75) False



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The sum of the measures of three angles of a triangle is always equal to 180°.

Q.76) It is possible to have a right angled equilateral triangle.

Sol.76) False In a right angled triangle, one angle is equal to 90° and in equilateral triangle, all angles are equal to 60°.

Q.77) If M is the mid-point of a line segment AB, then we can say that AM and MB are congruent

Sol.77) True Given, 𝑚 is the mid-point of a line segment AB 𝐴𝑀 = 𝑀𝐵 Two line segments are congruent that’s why they are of same lengths.

Q.78) It is possible to have a triangle in which two of the angles are right angles.

Sol.78) False If in a triangle two angles are right angles, then third angle = 180° − (90° + 90°) = 0°, which is not possible.

Q.79) It is possible to have a triangle in which two of the angles are obtuse.

Sol.79 False Obtuse angles are those angles which are greater than 90°. So, sum of two obtuse angles will be greater than 180°, which is not possible as the sum of all the angles of a triangle is 180°.

Q.80) It is possible to have a triangle in which two angles are acute.

Sol.80) True In a triangle, atleast two angles must be acute angle.

Q.81) It is possible to have a triangle in which each angle is less than 60°.

Sol.81) False The sum of all angles in a triangle is equal to 180°. So, all three angles can never be less than 60°.

Q.82) It is possible to have a triangle in which each angle is greater than 60°.

Sol.82) False If all the angles are greater than 60° in a triangle, then the sum of all the three angles with exceed 180°, which cannot be possible in case of triangle

Q.83) It is possible to have a triangle in which each angle is equal to 60°

Sol.83) True The triangle in which each angle is equal to 60° is called an equilateral triangle.

Q.84) A right angled triangle may have all sides equal.

Sol.84) False Hypotenuse is always the greater than the other two sides of the right angled triangle

Q.85) If two angles of a triangle are equal, the third angle is also equal to each of the other two angles.

Sol.85) False In an isosceles triangle, always two angles are equal and not the third one.

Q.86) In the given figures, two triangles are congruent by RHS.



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Sol.86) True

In ∆𝐴𝐵𝐶, 𝐴𝐶 = √𝐴𝐵2 + 𝐵𝐶2 = √42 + 52 = √41 cm

In ∆𝑃𝑄𝑅, 𝑃𝑅 = √𝑃𝑄2 + 𝑄𝑅2 = √42 + 52 = √41 cm Now, in ∆𝐴𝐵𝐶 and ∆𝑃𝑄𝑅, 𝐴𝐵 = 𝑃𝑄 = 4𝑐𝑚

𝐴𝐶 = 𝑃𝑅 = √41𝑐𝑚 ∠𝐴𝐵𝐶 = ∠𝑃𝑄𝑅 = 90° By RHS congruence criterion, ∆𝐴𝐵𝐶 ≅ ∆𝑃𝑄𝑅

Q.87) The congruent figures superimpose to each other completely.

Sol.87) True Because congruent figures have same shape and same size.

Q.88) A one rupee coin is congruent to a five rupees coin.

Sol.88) False Because they don’t have same shape and same size.

Q.89) The top and bottom faces of a kaleidoscope are congruent.

Sol.89) True Because they superimpose to each other.

Q.90) Two acute angles are congruent.

Sol.90) False Because the measure of two acute angles may be different.

Q.91) Two right angles are congruent.

Sol.91) True Since, the measure of right angles is always same.

Q.92) Two figures are congruent, if they have the same shape.

Sol.92) False Two figures are congruent, if they have the same shape and same size.

Q.93) If the areas of two squares is same, they are congruent.

Sol.93) True Because two squares will have same areas only if their sides are equal and squares with same sides will superimpose to each other

Q.94) If the areas of two rectangles are same, they are congruent.

Sol.94) False Because rectangles with the different length and breadth may have equal areas. But, they will not superimpose to each other.

Q.95) If the areas of two circles are the same, they are congruent.

Sol.95) True Because areas of two circles will be equal only if their radii are equal and circle with same radii will superimpose to each other.

Q.96) Two squares having same perimeter are congruent



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Sol.96) True If two squares have same perimeter, then their sides will be equal. Hence, the squares will superimpose to each other.

Q.97) Two circles having same circumference are congruent.

Sol.97) True If two circles have same circumference, then their radii will be equal. Hence, the circles will superimpose to each other.

Q.98) If three angles of two triangles are equal, triangles are congruent.

Sol.98) False Consider two equilateral triangles with different sides.

Both 𝛥𝐴𝐵𝐶 and 𝛥𝐷𝐸𝐹 have same angles but their size is different. So, they are not congruent

Q.99) If two legs of a right angled triangle are equal to two legs of another right angled triangle, then the right triangles are congruent.

Sol.99) True If two legs of a right angled triangle are equal to two legs of another right angled triangle, then their third leg will also be equal. Hence, they will have same shape and same size.

Q.100) If two sides and one angle of a triangle are equal to the two sides and angle of another triangle, then the two triangles are congruent.

Sol.100) False Because if two sides and the angle included between them of the other triangle, then the two triangles will be congruent.

Q.101) If two triangles are congruent, then the corresponding angles are equal

Sol.101) True Because if two triangles are congruent, then their sides and angles are equal.

Q.102) If two angles and a side of a triangle are equal to two angles and a side of another triangle, then the triangles are congruent.

Sol.102) False if two angles and the side included between them of a triangle are equal to two angles and included a side between them of the other triangle, then triangles are congruent.

Q.103) If the hypotenuse of one right triangle is equal to the hypotenuse of another right triangle, then the triangles are congruent.

Sol.103) False Two right angled triangles are congruent, if the hypotenuse and a side of one of the triangle are equal to the hypotenuse and one of the side of the other triangle.

Q.104) If hypotenuse and an acute angle of one right angled triangle are equal to the hypotenuse and an acute angle of another right angled triangle, then the triangles are congruent.



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Sol.104) True In ∆𝐴𝐵𝐶 and ∆𝑃𝑄𝑅,

∠𝐵 = ∠𝑄 = 90° ∠𝐶 = ∠𝑅 ∠𝐴 = ∠𝑃 Now, in ∆𝐴𝐵𝐶 and ∆𝑃𝑄𝑅, ∠𝐴 = ∠𝑃 𝐴𝐶 = 𝑃𝑅 ∠𝐶 = ∠𝑅 By ASA congruence criterion, ∆𝐴𝐵𝐶 ≅ ∆𝑃𝑄𝑅

Q.105) AAS congruence criterion is same as ASA congruence criterion.

Sol.105) False In ASA congruence criterion, the side ‘S’ included between the two angles of the triangle. In AAS congruence criterion, side ‘S’ is not included between two angles.

Q.106) In the given figure, AD⊥BC and AD is the bisector of angle BAC. Then, 𝛥𝐴𝐵𝐷 ≅ 𝛥𝐴𝐶𝐷 by RHS.

Sol.106) False

In ∆𝐴𝐵𝐷 and ∆𝐴𝐶𝐷, 𝐴𝐷 = 𝐴𝐷 ∠𝐵𝐴𝐷 = ∠𝐶𝐴𝐷 ∠𝐴𝐷𝐵 = ∠𝐴𝐷𝐶 = 90° By AASA congruence criterion, 𝛥𝐴𝐵𝐷 ≅ 𝛥𝐴𝐶𝐷

Q.107) The measure of three angles of a triangle are in the ratio 5:3:1. Find the measures of these angles.

Sol.107) Let measures of the given angles of a triangle be 5𝑥, 3𝑥 and 1𝑥. Sum of all the angles in a triangle = 180° 5𝑥 + 3𝑥 + 1𝑥 = 180° 9𝑥 = 180°

𝑥 =180°

9= 20°

So, the angles are 5𝑥 = 5 × 20 = 100°, 3𝑥 = 3 × 20 = 60° and 𝑥 = 20°

Q.108) In the given figure, find the value of 𝑥.

Sol.108) We know that, the sum of all three angles in a triangle is equal to 180°.

So, 𝑥 + 55° + 90° = 180° 𝑥 + 145° = 180°



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𝑥 = 180° − 145° 𝑥 = 35°

Q.109) In the given figures (i) and (ii), find the values of a, b and c.

Sol.109) In fig. (i), ∠𝐴 + ∠𝐵 + ∠𝐶 = 180°

90° + 𝑎 + 70° = 180° 𝑎 + 160° = 180° 𝑎 = 180° − 160° = 20° Since, 𝑐 is an exterior angle of ∆𝐴𝐵𝐷, ∠𝑐 = 𝑎 + 30° = 20° + 30° = 50° Also, 𝑏 is an exterior angle of ∆𝐴𝐷𝐶 ∠𝑏 = 60° + 70° = 130° In fig. (ii), In ∆𝑃𝑄𝑆, ∠𝑄𝑃𝑆 + ∠𝑃𝑄𝑆 + ∠𝑃𝑆𝑄 = 180° 55° + 60° + 𝑎 = 180° 115° + 𝑎 = 180° 𝑎 = 180° − 115° = 65° 𝑎 + 𝑏 = 180° 65° + 𝑏 = 180° 𝑏 = 180° − 65° = 115° In ∆𝑃𝑆𝑅, ∠𝑃𝑆𝑅 + ∠𝑆𝑃𝑅 + ∠𝑃𝑅𝑆 = 180° 115° + 𝑐 + 40° = 180° 𝑐 = 180° − 155° = 25°

Q.110) In 𝛥𝑋𝑌𝑍, the measure of ∠X is 30° greater than the measure of ∠Y and ∠Z is a right angle. Find measure of ∠Y.

Sol.110) According to the question, Measure of ∠X = ∠Y + 30 Measure of ∠Z = 90 The sum of all three angles in a triangle is equal to 180 ∠X + ∠Y + ∠Z = 180 ∠Y + (∠Y + 30) + 90° = 180 2∠Y + 120 = 180° 2∠Y = 180 − 120 = 60

∠Y =60

2= 30

Q.111) In a 𝛥𝐴𝐵𝐶, the measure of an ∠𝐴 is 40° less than the measure of other ∠B is 50° less than that of ∠C. Find the measure of ∠A.

Sol.111) According to the question, Measure of ∠𝐴 = ∠𝐵 − 40 Measure of ∠𝐶 = ∠𝐵 − 40 + 50 The sum of all 3 angles in a triangle is equal to 180 ∠𝐴 + ∠𝐵 + ∠𝐶 = 180 (∠𝐵 − 40) + ∠𝐵 + (∠𝐵 − 40 + 50) = 180



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3∠𝐵 − 30 = 180 3∠𝐵 = 210

∠𝐵 =210

3= 70

So, the measure of ∠𝐴 = 70 − 40 = 30

Q.112) I have three sides. One of my angle measures 15°. Another has a measure of 60°. What kind of a polygon am I? If I am a triangle, then what kind of triangle am I?

Sol.112) The polygon with three sides is called triangle. According to the angle sum property of a triangle ∠𝐴 + ∠𝐵 + ∠𝐶 = 180 ∠𝐴 + 15 + 60 = 180 ∠𝐴 = 180 − 75 = 105 As one angle in this triangle is greater than 90, so it is an obtuse angled triangle.

Q.113) Jiya walks 6 𝑘𝑚 due east and then 8 km due north. How far is she from her starting place?

Sol.113) As per the given information, we can draw the following figure, which is a right angled triangle at B. Distance from starting point to the final position in the hypotenuse of right angled ∆𝐴𝐵𝐶, 𝐴𝐶2 = 𝐴𝐵2 + 𝐵𝐶2 (6)2 + (8)2 = (𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒)2 36 + 64 = (𝑑𝑖𝑠𝑡𝑎𝑛𝑐𝑒)2

𝐷𝑖𝑠𝑡𝑎𝑛𝑐𝑒 = √100 = 10 𝑘𝑚 Q.114) Jayanti takes shortest route to her home by walking diagonally across a rectangular

park. The park measures 60 m x 80 m. How much shorter is the route across park than the route around its edges?

Sol.114) As the park is rectangular, all the angles are of 90 In right angled ∆𝐴𝐵𝐶, 𝐴𝐶2 = 𝐴𝐵2 + 𝐵𝐶2 𝐴𝐶2 = (60)2 + (80)2 = 3600 + 6400

𝐴𝐶2 = √10000 = 100 𝑚 If she goes through AB and AC, then total distance covered = (60 + 80)𝑚 = 140𝑚 Difference between two paths = (140 − 100)𝑚 = 40𝑚

Q.115) In 𝛥𝑃𝑄𝑅 of the given figure, 𝑃𝑄 = 𝑃𝑅. Find measures of ∠𝑄 and ∠𝑅.

Sol.115) Since, PQ=PR

∠𝑄 = ∠𝑅 = 𝑥 ∠𝑃 + ∠𝑄 + ∠𝑅 = 180 30 + 𝑥 + 𝑥 = 180 2𝑥 = 150

𝑥 =150

2= 75



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Hence, ∠𝑄 = ∠𝑅 = 75

Q.116) In the given figure, find the measures of ∠𝑥 and ∠𝑦.

Sol.116) Since, ∠𝑦 and 45 from a linear pair.

So, ∠𝑦 + 45 = 180 ∠𝑦 = 180 − 45 = 135 The sum of all angles in a triangle is equal to 180. So, 45 + 60 + ∠𝑥 = 180 105 + ∠𝑥 = 180 ∠𝑥 = 180 − 105 = 75

Q.117) In the given figure, find the measures of ∠PON and ∠NPO.

Sol.117) In ∆𝐿𝑂𝑀,

∠𝑂𝐿𝑀 + ∠𝑂𝑀𝐿 + ∠𝐿𝑂𝑀 = 180 70 + 20 + ∠𝐿𝑂𝑀 = 180 ∠𝐿𝑂𝑀 = 180 − 90 = 90 Also, ∠𝑃𝑂𝑁 = 90 In ∆𝑃𝑂𝑁, ∠𝑃𝑂𝑁 + ∠𝑁𝑃𝑂 + ∠𝑂𝑁𝑃 = 180 90 + ∠𝑁𝑃𝑂 + 70 = 180 ∠𝑁𝑃𝑂 = 180 − 160 = 120

Q.118) In the given figure, 𝑄𝑃 || 𝑅𝑇. Find the values of 𝑥 and 𝑦.

Sol.118) In the given figure, 𝑄𝑃|| 𝑅𝑇, where PR is a transversal line.

So, ∠𝑥 and ∠𝑇𝑅𝑃 are alternate interior angles

∠𝑥 = 70° The sum of all angle in a triangle is equal to 180° So, 45 + 60 + ∠𝑥 = 180 105 + ∠𝑥 = 180 ∠𝑥 = 180 − 105 = 75

Q.119) Find the measure of ∠𝐴 in the given figure.

Sol.119) As we know, the measure of exterior angle is equal to the sum of opposite interior



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angles. 115 = 65 + ∠𝐴 ∠𝐴 = 115 − 65 = 50

Q.120) In a right angled triangle, if an angle measures 35°, then find the measure of the third angle.

Sol.120) In a right angled 𝛥𝐴𝐵𝐶, ∠𝐴 + ∠𝐵 + ∠𝐶 = 180 ∠𝐴 + 90 + 35 = 180 ∠𝐴 + 125 = 180 ∠𝐴 = 180 − 125 = 55

Q.121) Each of the two equal angles of an isosceles triangle is four times the third angle. Find the angles of the triangle.

Sol.121) Let the third angle be x. Then, the other two angles are 4x and 4x, respectively. We know that, the sum of all three angles in triangle is 180. ∠𝐴 + ∠𝐵 + ∠𝐶 = 180 𝑥 + 4𝑥 + 4𝑥 = 180 9𝑥 = 180

𝑥 =180

9= 20

Hence, three angles are 4𝑥 = 4 × 20 = 80, 4𝑥 = 4 × 20 = 80 and 𝑥 = 20

Q.122) The angles of a triangle are in the ratio 2:3:5. Find the angles

Sol.122) Let measures of the given angles of a triangle be 2𝑥, 3𝑥 and 5𝑥 Sum of all the angles in a triangle = 180 2𝑥 + 3𝑥 + 5𝑥 = 180 10𝑥 = 180

𝑥 =180

10= 18

So, the angles are 2𝑥 = 2 × 18 = 36, 3𝑥 = 3 × 18 = 54 and 5𝑥 = 5 × 18 = 90

Q.123) If the sides of a triangle are produced in an order, show that the sum of the exterior angles so formed is 360°.

Sol.123) In ∆𝐴𝐵𝐶 by exterior angle property, Exterior ∠1 = interior ∠𝐴 + interior ∠𝐵 Exterior ∠2 =interior ∠𝐵 + interior ∠𝐶 Exterior ∠3 =interior ∠𝐴 +interior ∠𝐶 On adding eqs, (i), (ii) and (iii), we get ∠1 + ∠2 + ∠3 = 2(∠𝐴 + ∠𝐵 + ∠𝐶) [by angle sum property] ∠1 + ∠2 + ∠3 = 180 × 2 ∠1 + ∠2 + ∠3 = 360 Hence, sum of exterior angles is 360

Q.124) In 𝛥𝐴𝐵𝐶, if ∠𝐴 = ∠𝐶 and exterior ∠𝐴𝐵𝑋 = 140°, then find the angles of the triangle.

Sol.124) Given, ∠𝐴 = ∠𝐶 and exterior = ∠𝐴𝐵𝑋 = 140 Let ∠𝐴 = ∠𝐶 = 𝑥 According to exterior angle property, Exterior ∠𝐵 = interior ∠𝐴 +interior ∠𝐶 140 = 𝑥 + 𝑥 140 = 2𝑥



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𝑥 =140

2= 70

∠𝐴 = ∠𝐶 = 70 Now, ∠𝐴 + ∠𝐵 + ∠𝐶 = 180 70 + ∠𝐵 + 70 = 180 ∠𝐵 = 180 − 140 = 40 ∠𝐵 = 40 Hence, all the angles of the triangle are 70,40 and 70

Q.125) Find the values of 𝑥 and 𝑦 in the given figure.

Sol.125) In ∆𝑇𝑄𝑆, ∠𝑇 + ∠𝑄 + ∠𝑆 = 180

50 + 30 + ∠1 = 180 80 + ∠1 = 180 ∠1 = 180 − 80 = 100 ∠1 + 𝑥 = 180 100 + 𝑥 = 180 = 180 − 110 𝑥 = 80 In ∆𝑇𝑆𝑅, 𝑥 + 45 + ∠2 = 180 ∠2 = 180 − 80 − 45 = 55 50 + ∠2 + 𝑦 = 180 𝑦 = 180 − 50 − 55 = 75

Q.126) Find the value of 𝑥 in the given figure.

Sol.126) In the given figure, ∠𝐵𝐴𝐶 = 80, ∠𝐴𝐵𝐶 = 30, ∠𝐴𝐶𝐸 = 𝑥 and ∠𝐸𝐶𝐷 = 90 In ∆𝐴𝐵𝐶, we know that, exterior angle is equal to the sum of exterior opposite angles.

∠𝐴𝐶𝐷 = ∠𝐶𝐴𝐵 + ∠𝐴𝐵𝐶 ∠𝐴𝐶𝐸 + ∠𝐸𝐶𝐷 = 80 + 30 ∠𝐴𝐶𝐸 + 90 = 110 ∠𝐴𝐶𝐸 = 110 − 90 = 20

Q.127) The angles of a triangle are arranged in descending order of their magnitudes. If the difference between two consecutive angles is 10°, find the three angles

Sol.127) Let one of the angles of a triangle be x. If angles are arranged in descending order.

Then, angles will be 𝑥, (𝑥 − 10°) and (𝑥 – 20°). We know that, the sum of all angles in a triangle is equal to 180 So, 𝑥 + (𝑥 − 10) + (𝑥 − 20) = 180 𝑥 + 𝑥 + 𝑥 − 30 = 180 3𝑥 = 180 + 30 3𝑥 = 210

𝑥 =210

3= 70

Hence, angles will be 70, 70 − 10 and 70 − 20 i.e., 70,60 and 50.



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Q.128) In 𝛥𝐴𝐵𝐶, 𝐷𝐸 || 𝐵𝐶 (see the figure). Find the values of 𝑥, 𝑦 and 𝑧.

Sol.128) In ∆𝐴𝐵𝐶, ∠𝐴 + ∠𝐵 + ∠𝐶 = 180 𝑧 + 30 + 40 = 180 𝑧 + 70 = 180 𝑧 = 180 − 70 = 110 𝐷𝐸 || 𝐵𝐶 Now, ∠𝐴𝐷𝐸 = ∠𝐴𝐵𝐶 ∠𝑥 = 30 and ∠𝐴𝐸𝐷 = ∠𝐴𝐶𝐵 ∠𝑦 = 40

Q.129) In the given figure, find the values of 𝑥, 𝑦 and 𝑧.

Sol.129) In the given figure, ∠𝐵𝐴𝐷 = 60, ∠𝐴𝐵𝐷 = 60, ∠𝐴𝐷𝐵 = 𝑥, ∠𝐷𝐴𝐶 = 30, ∠𝐴𝐷𝐶 = 𝑦

and ∠𝐴𝐶𝐷 = 𝑧 We know that, the sum of all angles in a triangle is equal to 180 In ∆𝐴𝐵𝐷, ∠𝐵𝐴𝐷 + ∠𝐴𝐵𝐷 + ∠𝐴𝐷𝐵 = 180 60 + 60 + 𝑥 = 180 120 + 𝑥 = 180 𝑥 = 180 − 120 = 60 𝑦 = ∠𝐵𝐴𝐷 + ∠𝐴𝐵𝐷 𝑦 = 60 + 60 𝑦 = 120 In ∆𝐴𝐷𝐶, ∠𝐷𝐴𝐶 + ∠𝐴𝐷𝐶 + ∠𝐴𝐶𝐷 = 180 30 + 120 + 𝑧 = 180 150 + 𝑧 = 180 𝑧 = 180 − 150 = 30 Hence, 𝑥 = 60, 𝑦 = 120 and 𝑧 = 30

Q.130) If one angle of a triangle is 60° and the other two angles are in the ratio 1: 2, find the angles.

Sol.130) Given, one angle of a triangle is 60 Let the other two angles be 𝑥 and 2𝑥 We know, the sum of all angles in a triangle is equal to 180 So, 𝑥 + 2𝑥 + 60 = 180 3𝑥 = 180 − 60 3𝑥 = 120

𝑥 =120

3= 40

So, the other two angles will be 𝑥 = 40 and 2𝑥 = 2 × 40 = 80

Q..131) In 𝛥𝑃𝑄𝑅, if 3∠𝑃 = 4∠𝑄 = 6∠𝑅, calculate the angles of the triangle.

Sol.131) Given, 3∠𝑃 = 4∠𝑄 = 6∠𝑅

Then, ∠𝑃 =6

3∠𝑅 = 2∠𝑅

∠𝑄 =6

4∠𝑅 =

3

2∠𝑅



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In ∆𝑃𝑄𝑅, ∠𝑃 + ∠𝑄 + ∠𝑅 = 180

2∠𝑅 +3

2∠𝑅 + ∠𝑅 = 180

3∠𝑅 +3

2∠𝑅 = 180

6∠𝑅 + 3∠𝑅 = 180 × 2 9∠𝑅 = 360

∠𝑅 =360

9= 40

∠𝑃 = 2∠𝑅 = 2 × 40 = 80

∠𝑄 =3

2∠𝑅 =

3

2× 40 = 60

Hence, all the angles of the triangle are 80, 60 and 40

Q132) In 𝛥𝐷𝐸𝐹, ∠𝐷 = 60°, ∠𝐸 = 70° and the bisectors of ∠𝐸 and ∠𝐸 meet at O. Find (i) ∠𝐹 (ii) ∠𝐸𝑂𝐹

Sol.132)

(i) As we know, ∠𝐷 + ∠𝐸 + ∠𝐹 = 180 60 + 70 + ∠𝐹 = 180 ∠𝐹 = 180 − 130 = 50 ii) Now, as FO is the bisector of ∠𝐹

so, ∠𝐸𝐹𝑂 =∠𝐹

2=

50

2= 25

and ∠𝑂𝐸𝐹 =∠𝐸

2=

70

2= 35

In ∆𝐸𝑂𝐹, ∠𝐸𝑂𝐹 + ∠𝑂𝐸𝐹 + ∠𝑂𝐹𝐸 = 180 ∠𝐸𝑂𝐹 + 35 + 25 = 180 ∠𝐸𝑂𝐹 = 180 − 60 = 120

Q.133) In the given figure, 𝛥𝑃𝑄𝑅 is right angled at P. U and T are the points on line 𝑄𝑅𝐹. If 𝑄𝑃 || 𝑆𝑇 and 𝑈𝑆 || 𝑅𝑃, find ∠𝑆.

Sol.133) If 𝑄𝑃 || 𝑆𝑇 and 𝑄𝑇 is a transversal, then ∠𝑃𝑄𝑅 = ∠𝑆𝑇𝑈 [alternate interior angles]

and if 𝐷𝑆 || 𝑅𝑃 and 𝑄𝑇 is a transversal, then ∠𝑃𝑅𝑄 = ∠𝑆𝑈𝑇 [alternate interior angles] Hence, ∠𝑆 must be equal to ∠𝑃 i.e. 90°.

Q.134) In each of the given pairs of triangles in given figures, applying only ASA congruence criterion, determine which triangles are congruent. Also, write the congruent triangles in symbolic form.



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Sol.134) (a) Not possible, because the side is not included between two angles.

(b) ∆𝐴𝐵𝐷 ≅ ∆𝐶𝐷𝐵 (c) ∆𝑋𝑌𝑍 ≅ ∆𝐿𝑀𝑁 (d) Not possible, because there is not any included side equal. (e) ∆𝑀𝑁𝑂 ≅ ∆𝑃𝑂𝑁 (f) ∆𝐴𝑂𝐷 ≅ ∆𝐵𝑂𝐶

Q.135) In each of the given pairs of triangles in given figures, using only RHS congruence criterion, determine which pairs of triangles are congruent. In case of congruence, write the result in symbolic form,

Sol.135) a) In ∆𝐴𝐵𝐷 and ∆𝐴𝐶𝐷,

𝐴𝐷 = 𝐴𝐷 ∠𝐴𝐷𝐵 = ∠𝐴𝐷𝐶 = 90 By RHS congruence criterion, ∆𝐴𝐵𝐷 ≅ ∆𝐴𝐶𝐷 b) In ∆𝑋𝑌𝑍 and ∆𝑈𝑍𝑌, ∠𝑋𝑌𝑍 = ∠𝑈𝑍𝑌 = 90 𝑋𝑍 = 𝑌𝑈 𝑍𝑌 = 𝑍𝑌 By RHS congruence criterion, ∆𝑋𝑌𝑍 ≅ ∆𝑈𝑍𝑌 = 90 c) In ∆𝐴𝐸𝐶 and ∆𝐵𝐸𝐷, 𝐶𝐸 = 𝐷𝐸 𝐴𝐸 = 𝐵𝐸 ∠𝐴𝐶𝐸 = ∠𝐵𝐷𝐸 = 90 By RHS congruence criterion, ∆𝐴𝐸𝐶 ≅ ∆BED d) Here, 𝐶𝐷 = 𝐵𝐷 − 𝐵𝐶 = 14 − 8 = 6𝑐𝑚 in right angled, ∆𝐴𝐵𝐶

𝐴𝐶 = √𝐴𝐵2 + 𝐵𝐶2 = √62 + 82 = √36 + 64

= √100 = 10𝑐𝑚



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In right angled ∆𝐶𝐷𝐸,

𝐷𝐸 = √𝐶𝐸2 − 𝐶𝐷2 = √102 − 62

= √100 − 36 = √64 = 8𝑐𝑚 In ∆𝐴𝐵𝐶 and ∆𝐶𝐷𝐸, 𝐴𝐶 = 𝐶𝐸 = 10𝑐𝑚 𝐵𝐶 = 𝐷𝐸 = 8𝑐𝑚 ∠𝐴𝐵𝐶 = ∠𝐶𝐷𝐸 = 90 By RHS congruence criterion, ∆𝐴𝐵𝐶 ≅ ∆𝐶𝐷𝐸 e) Not possible, because there is not any right angle. f) In ∆𝐿𝑂𝑀 and ∆𝐿𝑂𝑁, 𝐿𝑀 = 𝐿𝑁 = 8𝑐𝑚 𝐿𝑂 = 𝐿𝑂 ∠𝐿𝑂𝑀 = ∠𝐿𝑂𝑁 = 90 By RHS congruence criterion, ∆𝐿𝑂𝑀 ≅ ∆𝐿𝑂𝑁

Q.136) In the given figure, if RP = RQ, find the value of 𝑥.

Sol.136) Given, 𝑅𝑃 = 𝑅𝑄

Since, ∠1 = 50 Also, ∠1 = 𝑥 So, 𝑥 = 50

Q.137) In the given figure, if ST = SU, then find the values of x and y.

Sol.137) Given, 𝑆𝑇 = 𝑆𝑈

∠𝑆𝑈𝑇 = ∠𝑆𝑇𝑈 = 𝑦 Also, ∠1 = 78 In ∆𝑆𝑈𝑇, 78 + 𝑦 + 𝑦 = 180 78 + 2𝑦 = 180 2𝑦 = 180 − 78 = 102

𝑦 =102

2= 51

Also, 𝑥 + 𝑦 = 180 𝑥 + 51 = 180



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𝑥 = 180 − 51 = 129 Q.138) Check whether the following measures (in cm) can be the sides of a right angled

triangle or not. 1.5, 3.6, 3.9

Sol.138) For a right angled triangle, the sum of square of two shorter sides must be equal to the square of the third side. Now, 1.52 + 3.62 = 2.25 + 12.96 = 15.21 (3.9)2 = 15.21 (1.5)2 + (3.6)2 = (3.9)2 Hence, the given sides form right angled triangle.

Q.139) Height of a pole is 8 m. Find the length of rope tied with its top from a point on the ground at a distance of 6 m from its bottom.

Sol.139) Given, height of a pole is 8 m. Distance between the bottom of the pole and a point on the ground is 6 m. On the basis of given information, we can draw the following figure:

Let the length of the rope be 𝑥 𝑚 𝐴𝐵 = height of the pole 𝐵𝐶 = Distance between the bottom of the pole and a point on ground, where rope was tied To find length of the rope, we will use Pythagoras theorem, in right angled ∆𝐴𝐵𝐶 (𝐴𝐶)2 = (𝐴𝐵)2 + (𝐵𝐶)2 (𝑥)2 = (8)2 + (6)2 𝑥2 = 100

𝑥 = √100 = 10𝑚 Hence, the length of the rope is 10 m.

Q.140) In the given figure, if 𝑦 is five times 𝑥, find the value of 𝑧.

Sol.140) Given, 𝑦 = 5𝑥

According to the angle sum property of a triangle 60 + 𝑥 + 𝑦 = 180 60 + 𝑥 + 5𝑥 = 180 60 + 6𝑥 = 180 6𝑥 = 180 − 60 = 120

𝑥 =120

6= 20

𝑦 = 5𝑥 = 5 × 20 = 100 According to the exterior angle property, 𝑧 = 60 + 𝑦



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= 60 + 100 = 160

Q.141) The lengths of two sides of an isosceles triangle are 9 cm and 20 cm. What is the perimeter of the triangle? Give reason.

Sol.141) Third side must be 20 cm, because sum of two sides should be greater than the third side. ∴ Perimeter of the triangle = Sum of all sides = (9 + 20 + 20) 𝑐𝑚 = 49 𝑐𝑚

Q.142) Without drawing the triangles write all six pairs of equal measures in each of the following pairs of congruent triangles. (a) 𝛥𝑆𝑇𝑈 ≅ 𝛥𝐷𝐸𝐹 (b) 𝛥𝐴𝐵𝐶 ≅ 𝛥𝐿𝑀𝑁 (c) 𝛥𝑌𝑍𝑋 ≅ ∆𝑃𝑄𝑅 (d) 𝛥𝑋𝑌𝑍 ≅ 𝛥𝑀𝐿𝑁

Sol.142) We know that, corresponding parts of congruent triangles are equal. (a) 𝛥𝑆𝑇𝑈 ≅ 𝛥𝐷𝐸𝐹 ∠𝑆 = ∠𝐷, ∠𝑇 = ∠𝐸 and ∠𝑈 = ∠𝐹 𝑆𝑇 = 𝐷𝐸, 𝑇𝑈 = 𝐸𝐹 and SU = DF (b) 𝛥𝐴𝐵𝐶 ≅ 𝛥𝐿𝑀𝑁 ∠𝐴 = ∠𝐿, ∠𝐵 = ∠𝑀 𝑎𝑛𝑑 ∠𝐶 = ∠𝑁 𝐴𝐵 = 𝐿𝑀, 𝐵𝐶 = 𝑀𝑁 and AC = LN (c) 𝛥𝑌𝑍𝑋 ≅ 𝐴𝑃𝑄𝑅 ∠𝑇 = ∠𝑃, ∠𝑍 = ∠𝑄 and ∠𝑋 = ∠𝑅 𝑌𝑍 = 𝑃𝑄, 𝑍𝑋 = 𝑄𝑅 and YX = PR (d) 𝛥𝑋𝑌𝑍 ≅ 𝛥𝑀𝐿𝑁 ∠𝑋 = ∠𝑀, ∠𝑌 = ∠𝐿 𝑎𝑛𝑑 ∠𝑍 = ∠𝑁 𝑋𝑌 = 𝑀𝐿, 𝑌𝑍 = 𝐿𝑁 and XZ = MN

Q.143) In the following pairs of triangles in below figures, the lengths of the sides are indicated along the sides. By applying SSS congruence criterion, determine which triangles are congruent. If congruent, write the results in symbolic form.

Sol.143) (a) 𝛥𝐴𝐵𝐶 ≅ 𝛥𝑁𝐿𝑀 (b) 𝛥𝐿𝑀𝑁 ≅ 𝛥𝐺𝐻𝐼

(c) 𝛥𝐿𝑀𝑁 ≅ 𝛥𝐿𝑂𝑁 (d) 𝛥𝑍𝑌𝑋 ≅ 𝛥𝑊𝑋𝑌 (e) 𝛥𝑂𝐴𝐵 ≅ 𝛥𝐷𝑂𝐸 (f) 𝛥𝑆𝑇𝑈 ≅ 𝛥𝑆𝑉𝑈 (g) 𝛥𝑃𝑆𝑅 ≅ ∆𝑅𝑄𝑃 (h) 𝛥𝑆𝑇𝑈 ≅ 𝛥𝑃𝑄𝑅

Q.144) ABC is an isosceles triangle with AB = AC and D is the mid-point of base BC (see the figure).



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(a) State three pairs of equal parts in the 𝛥𝐴𝐵𝐷 and 𝛥𝐴𝐶𝐷. (b) Is 𝛥𝐴𝐵𝐷 ≅ 𝛥𝐴𝐶𝐷? If so why?

Sol.144) Given, 𝐴𝐵 = 𝐴𝐶 And 𝐵𝐷 = 𝐶𝐷 a) In ∆𝐴𝐵𝐷 and ∆𝐴𝐶𝐷 𝐴𝐵 = 𝐴𝐶 𝐵𝐷 = 𝐶𝐷 𝐴𝐷 = 𝐴𝐷 b) Yes, by SSS congruence criterion, 𝛥𝐴𝐵𝐷 ≅ 𝛥𝐴𝐶𝐷

Q.145) In the given figure, it is given that LM = ON and NL = MO.

(a) State the three pairs of equal parts in the ∆𝑁𝑂𝑀 and ∆𝑀𝐿𝑁. (b) Is ∆𝑁𝑂𝑀 ≅ ∆𝑀𝐿𝑁? Give reason

Sol.145) a) In ∆𝑁𝑂𝑀 and ∆𝑀𝐿𝑁, 𝐿𝑀 = 𝑂𝑁 𝑀𝑁 = 𝑀𝑁 𝐿𝑁 = 𝑂𝑀 b) Yes, by SSS congruence criterion, ∆𝑁𝑂𝑀 ≅ ∆𝑀𝐿𝑁

Q.146) 𝛥𝐷𝐸𝐹 and 𝛥𝐿𝑀𝑁 are both isosceles with DE = DF and LM = LN, respectively. If DE = LM and 𝐸𝐹 = 𝑀𝑁, then are the two triangles congruent? Which condition do you use? If ∠𝐸 = 40°, what is the measure of ∠𝑁?

Sol.146) Here, 𝐷𝐸 = 𝐷𝐹 …(i) 𝐿𝑀 = 𝐿𝑁 …(ii) 𝐷𝐸 = 𝐿𝑀 …(iii) From eqs. (i), (ii) and (iii), we get 𝐷𝐸 = 𝐷𝐹 = 𝐿𝑀 = 𝐿𝑁 In ∆𝐷𝐸𝐹 and ∆𝐿𝑀𝑁, 𝐷𝐸 = 𝐿𝑀 𝐸𝐹 = 𝑀𝑁 𝐷𝐹 = 𝐿𝑁 By SSS congruence criterion, ∆𝐷𝐸𝐹 ≅ ∆𝐿𝑀𝑁 ∠𝐸 = ∠𝑀 ∠𝑀 = 40 Also, ∠𝑀 = ∠𝑁 ∠𝑁 = 40

Q.147) If ΔPQR and ΔSQR are both isosceles triangle on a common base QR such that P and S



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lie on the same side of QR. Are 𝛥𝑃𝑆𝑄 and 𝛥𝑃𝑆𝑅 congruent? Which condition do you use?

Sol.147) In ∆𝑃𝑆𝑄 and ∆𝑃𝑆𝑅 𝑃𝑄 = 𝑃𝑅 𝑆𝑄 = 𝑆𝑅 𝑃𝑆 = 𝑃𝑆 By SSS congruence criterion, ∆𝑃𝑆𝑄 ≅ ∆𝑃𝑆𝑅

Q.148) In the given figures, which pairs of triangles are congruent by SAS congruence criterion (condition)? If congruent, write the congruence of the two triangles in symbolic form.

Sol.148) i) In ∆𝑃𝑄𝑅 and ∆𝑇𝑈𝑆,

𝑃𝑄 = 𝑇𝑈 = 3𝑐𝑚 𝑄𝑅 = 𝑈𝑆 = 5.5𝑐𝑚 ∠𝑃𝑄𝑅 = ∠𝑇𝑈𝑆 = 40 By SAS congruence criterion, ∆𝑃𝑄𝑅 ≅ ∆𝑇𝑈𝑆 ii) Not possible, because angle is not included between two sides. Iii) In ∆𝐵𝐶𝐷 and ∆𝐵𝐴𝐸, 𝐴𝐵 = 𝐶𝐵 = 5.2𝑐𝑚 𝐷𝐶 = 𝐸𝐴 = 5𝑐𝑚 ∠𝐸𝐴𝐵 = ∠𝐷𝐶𝐵 = 50 By SAS congruence criterion, ∆𝐵𝐶𝐷 ≅ ∆𝐵𝐴𝐸 iv) In ∆𝑆𝑇𝑈 and ∆𝑋𝑍𝑌, 𝑇𝑈 = 𝑍𝑌 = 4𝑐𝑚



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𝑇𝑆 = 𝑍𝑋 = 3𝑐𝑚 ∠𝑆𝑇𝑈 = ∠𝑋𝑍𝑌 = 30 By SAS congruence criterion, ∆𝑆𝑇𝑈 ≅ ∆𝑋𝑍𝑌 v) In ∆𝐷𝑂𝐹 and ∆𝐻𝑂𝐶, 𝐷𝑂 = 𝐻𝑂 𝐶𝑂 = 𝐹𝑂 ∠𝐷𝑂𝐹 = ∠𝐻𝑂𝐶 By SAS congruence criterion, ∆𝐷𝑂𝐹 ≅ ∆𝐻𝑂𝐶 vi) Not congruent, because angle is not included between two sides vii) In ∆𝑃𝑆𝑄 and ∆𝑅𝑄𝑆, 𝑃𝑆 = 𝑄𝑆 = 4𝑐𝑚 𝑆𝑄 = 𝑆𝑄 ∠𝑃𝑆𝑄 = ∠𝑅𝑄𝑆 = 40 By SAS congruence criterion, ∆𝑃𝑆𝑄 ≅ ∆𝑅𝑄𝑆 viii) In ∆𝐿𝑀𝑁 and ∆𝑂𝑀𝑁, 𝐿𝑀 = 𝑂𝑀 𝑀𝑁 = 𝑀𝑁 ∠𝐿𝑀𝑁 = ∠𝑂𝑀𝑁 = 40 By SAS congruence criterion, ∆𝐿𝑀𝑁 ≅ ∆𝑂𝑀𝑁

Q.149) State which of the following pairs of triangles are congruent. If yes, write them in symbolic form (you may draw a rough figure). (a) 𝛥𝑃𝑄𝑅 ∶ 𝑃𝑄 = 3.5 𝑐𝑚, 𝑄𝑅 4.0 𝑐𝑚, ∠𝑄 60° 𝛥𝑆𝑇𝑈 ∶ 𝑆𝑇 = 3.5 𝑐𝑚, 𝑇𝑈 = 4 𝑐𝑚, ∠𝑇 = 60° (b) 𝛥𝐴𝐵𝐶 ∶ 𝐴𝐵 = 4.8 𝑐𝑚, ∠𝐴 = 90°, 𝐴𝐶 = 6.8 𝑐𝑚 𝛥𝑋𝑌𝑍 ∶ 𝑌𝑍 = 6.8 𝑐𝑚, ∠𝑋 = 90°, 𝑍𝑋 = 4.8 𝑐𝑚

Sol.149) a) Both the triangles are congruent ∆𝑃𝑄𝑅 ≅ ∆𝑆𝑇𝑈

b) Both the triangles are not congruent.

Q.150) In the given figure, PQ = PS and ∠1 = ∠2.



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(i) Is 𝛥𝑃𝑄𝑅 ≅ 𝛥𝑃𝑆𝑅? Give reason. (ii) Is 𝑄𝑅 = 𝑆𝑅? Give reason.

Sol.150) Yes i) In ∆𝑃𝑄𝑅 and ∆𝑃𝑆𝑅, 𝑃𝑄 = 𝑃𝑆 ∠1 = ∠2 By SAS congruence criterion, ∆𝑃𝑄𝑅 ≅ ∆𝑃𝑆𝑅 ii) Yes, 𝑄𝑅 = 𝑆𝑅

Q.151) In the given figure, 𝐷𝐸 = 𝐼𝐻, 𝐸𝐺 = 𝐹𝐼 and ∠𝐸 = ∠𝐼. Is 𝛥𝐷𝐸𝐹 ≅ 𝛥𝐻𝐼𝐺? If yes, by which congruence criterion?

Sol.151) Given, 𝐸𝐺 = 𝐹𝐼

𝐸𝐺 + 𝐺𝐹 = 𝐹𝐼 + 𝐺𝐹 In ∆𝐷𝐸𝐹 and ∆𝐻𝐼𝐺, 𝐷𝐸 = 𝐼𝐻 𝐸𝐹 = 𝐼𝐺 ∠𝐸 = ∠𝐼 By SAS congruence criterion, ∆𝐷𝐸𝐹 ≅ ∆𝐻𝐼𝐺

Q.152) In the given figure, ∠1 = ∠2 and ∠3 = ∠4.

(i) Is 𝛥𝐴𝐷𝐶 ≅ 𝛥𝐴𝐵𝐶 Why? Show that AD = AB and CD = CB

Sol.152) i) In ∆𝐴𝐷𝐶 and ∆𝐴𝐵𝐶, ∠1 = ∠2 𝐴𝐶 = 𝐴𝐶 ∠3 = ∠4 By ASA congruence criterion, ∆𝐴𝐷𝐶 ≅ ∆𝐴𝐵𝐶 ii) 𝐴𝐷 = 𝐴𝐵



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𝐶𝐷 = 𝐶𝐵 Q.153) Observe the following figure and state the three pairs of equal parts in ΔABC and

𝛥𝐷𝐵𝐶.

(i) Is 𝛥𝐴𝐵𝐶 ≅ 𝛥𝐷𝐶𝐵? Why? (ii) Is 𝐴𝐵 = 𝐷𝐶? Why? (iii) Is 𝐴𝐶 = 𝐷𝐵? Why?

Sol.153) i) In ∆𝐴𝐵𝐶 and ∆𝐷𝐶𝐵, 𝐵𝐶 = 𝐵𝐶 ∠𝐴𝐵𝐶 = ∠𝐷𝐶𝐵 = 70 ∠𝐴𝐶𝐵 = ∠𝐷𝐵𝐶 = 30 By ASA congruence criterion, ∆𝐴𝐵𝐶 ≅ ∆𝐷𝐶𝐵 . ii) AB = DC [by CPCT] iii) AC = DB [by CPCT]

Q.154) In the given figure, 𝑄𝑆 ⊥ 𝑃𝑅, 𝑅𝑇 ⊥ 𝑃𝑄 and 𝑄𝑆 = 𝑅𝑇.

(i) Is 𝛥𝑄𝑆𝑅 ≅ 𝛥𝑅𝑇𝑆? Give reason. (ii) Is ∠𝑃𝑄𝑅 = ∠𝑃𝑅𝑄? Give reason.

Sol.154) i) In ∆𝑄𝑆𝑅 and ∆𝑅𝑇𝑄, 𝑄𝑆 = 𝑅𝑇 ∠𝑄𝑆𝑅 = ∠𝑄𝑇𝑅 = 90 𝑄𝑅 = 𝑄𝑅 By RHS congruence criterion, ∆𝑄𝑆𝑅 ≅ ∆𝑅𝑇𝑄 ii) Yes, ∠𝑃𝑄𝑅 = ∠𝑃𝑅𝑄

Q.155) Points A and B are on the opposite edges of a pond as shown in the given figure. To find the distance between the two points, the surveyor makes a right angled triangle as shown. Find the distance AB.

Sol.155) Since, ∆𝐴𝐶𝐷 is a right angled triangle.

Right angled ∆𝐴𝐷𝐶, by Pythagoras theorem, (𝐴𝐶)2 = (𝐴𝐷)2 + (𝐶𝐷)2



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(𝐴𝐶)2 = (30)2 + (40)2 (𝐴𝐶)2 = 900 + 1600 (𝐴𝐶)2 = 2500

𝐴𝐶 = √2500 = 50𝑚 Now, 𝐴𝐵 = 𝐴𝐶 − 𝐵𝐶 = 50 − 12 = 38𝑚 Hence, distance AB is 38 m

Q.156) Two poles of 10 m and 15 m stand upright on a plane ground. If the distance between the tops is 13 m, find distance between their feet.

Sol.156) Let 𝐵𝐶 = 𝑥𝑚 In right angled ∆𝐴𝐶𝐵, 𝐴𝐵2 = 𝐴𝐶2 + 𝐵𝐶2 (13)2 = (5)2 + (𝑥)2 169 − 25 = 𝑥2 144 = 𝑥2

𝑥 = √144 𝑥 = 12𝑚 Hence, distance between the feet of two poles is 12 𝑚

Q.157) The foot of a ladder is 6 m away from its wall and its top reaches a window 8 m above the ground, (a) Find the length of the ladder, (b) If the ladder is shifted in such a way that its foot is 8 m away from the wall, to what height does its top reach?

Sol.157) a) Let the length of the ladder be 𝑥 𝑚 In the right angled ∆𝐴𝐵𝐶, 𝐴𝐶2 = 𝐴𝐵2 + 𝐵𝐶2 (𝑥)2 = (8)2 + (6)2

= 64 + 36 = √100 𝑥 = 10 𝑚 Hence, the length of the ladder is 10 m b) Let the height of the top be 𝑥 𝑚 In right angled ∆𝐴𝐶𝐵, 𝐴𝐶2 = 𝐴𝐵2 + 𝐵𝐶2 𝐴𝐵2 = 𝐴𝐶2 − 𝐵𝐶2 (𝑥)2 = (10)2 + (8)2

= 100 + 64 = √36 𝑥 = 6 𝑚 Hence, the height of the top is 6 m

Q.158) In the given figure, state the three pairs of equal parts in ΔABC and ΔEOD. Is ΔABC ≅ ΔEOD? Why?

Sol.158) In ∆𝐴𝐵𝐶 and ∆𝐸𝑂𝐷,



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𝐴𝐵 = 𝐸𝑂 𝐴𝐶 = 𝐸𝐷 ∠𝐴𝐵𝐶 = ∠𝐸𝑂𝐷 = 90 By RHS congruence criterion, ∆𝐴𝐵𝐶 ≅ ∆𝐸𝑂𝐷



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Documents

(a) 25 m (b) 13 m (c) 18 m (d) 17 m Sol.11) (c) Let AB be the given that tree of height h m, which is broken at D which is 12 m away from its base and the height of remaining part,