• Before the bell rings...– Copy the weekly planner.– Have your covered textbook with you.

1. Put these in order for least to greatest. ¾ 2/3 5/8 5/7

2. Anna saw 171 fish during her 38-minute drive. At this rate, how many did she see in the first two minutes?

• Before the bell rings...– Copy the weekly planner.– Have your covered textbook with you.

1. Put these in order for least to greatest. ¾ 2/3 5/8 5/7

2. Anna saw 171 fish during her 38-minute drive. At this rate, how many did she see in the first two minutes?

5/8, 2/3, 5/7, 3/4

9 fish

Fractions

Adding and Subtracting

Essential Questions

1. What is the value of studying fractions?

2. What is the relationship between good number sense and working with fractions?

Rule for +, -

• Must have or get

COMMON DENOMINATORS

Add or subtract only the numerators, keeping the same denominator.

Simplify fraction into lowest terms

3

52

3

1)Find the LCM

2)Find the new numerators

3)Add the numerators

4)Simplify the fraction

15

10

15

19

15

41

15

9

• Subtract

4

52

7

1.Find the LCM2.Find the new numerators3.Subtract the numerators4.Simplify the fraction

35

28

35

10

35

18

Try these examples

2 37 5

3 4

39 2

5

12

95

12

87

=

= =12

1712 =

12

513

5

32

5

58 =

5

26

More examples

24

96

36

82

43

24

164

24

335

24

164

24

171

EXAMPLE 1 Adding and Subtracting Fractions

a. 78 + – 2

5 =3540

– 1640+ Rewrite fractions using LCD of 40.

=35 +( – 16)

40Write sum over LCD.

1940= Evaluate numerator.

b. 310

56

– = 930

2530

– Rewrite fractions using LCD of 30.

=9 – 25

30Write difference over LCD.

=– 1630

Evaluate numerator.

815

–= Simplify.

GUIDED PRACTICE for Example 1

Find the sum or difference. Then simplify if possible.2. 3

49

10– = 30

403640

– Rewrite fractions using LCD of 40.

=30 – 36

40Write difference over LCD.

– 640= Evaluate numerator.– 3

20=3

20

GUIDED PRACTICE for Example 1

Find the sum or difference. Then simplify if possible.3. 5

12– 79

+ = 45108

– 84108

+ Rewrite fractions using LCD of 108.

=45 – 84

108Write sum over LCD.

– 39108= Evaluate numerator.

13

36

1336=–

GUIDED PRACTICE for Example 1

Find the sum or difference. Then simplify if possible.5. 1

61115

– = 1590

6690

– Rewrite fractions using LCD of 90.

=15 – 66

90Write difference over LCD.

– 5190= Evaluate numerator.

– 1730= Simplify.

Homework

• Page 240 #1-13, 36-39