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MENSURATION
1. Need for standard units.
2. Formulae for some geometrical figures.
3. Applications.
. POINT
LINE SEGMENT
How do we measure it?
The standard unit of length is meter.
The smaller units are mm, cm, dm.
1 UNIT
REGION ENCLOSED BY PLANE FIGURES
Which of the following
encloses more region?
The amount of region enclosed by any plane figure is called its AREA
Its area is 1 cm2
So area is measured in square units
Let us recall
l x b a2 ½ bh
bhπ r2
½π r2
2 (l +b) 4a
2π r
Perimeter
2r
π r
π r + 2r
Area of Rhombus
b
h
Area = bh
d1
d2
Area = ½ d1d2
h1
h2A
B
CD
Area of a general Quadrilateral
Area = ½ AC ( h1 + h2 )
B
A
CD
3cm
5cm8cm
Area = ½ x 8 x ( 3 + 5 ) = 4 x 8 = 32 cm2
a
b
h
TRAPEZIUMA quadrilateral with one pair of
opposite sides parallel
How to find the area of a trapezium ?
lengths of parallel sides -- a & b
Distance between parallel sides - h
Area of trapezium =
1/2 * (Sum of parallel sides) *Distance between them
Area = ½ * (a + b ) * h
Find the area of the given trapezium.
6 cm
10 cm
5 cm
a = 10 cm , b = 6 cm , h = 5 cm
Area = ½ * ( a + b ) * h
= 1 /2* ( 10 + 6 ) * 5 = 1/2 * ( 1 6 ) * 5
= 8 * 5 = 40 cm2
Calculate the area of the given trapezium ABCD in which AB // CD , AB = 16cm , CD = 12cm and the distance between AB & CD is 15cm
A B
CD
ASSIGNMENT