Page 27 - Maths Skills - 7

Fractions and Decimals 25

ADDITION AND SUBTRACTION OF LIKE FRACTIONS
1. Addition of like fractions
5
Step 1. Add the numerators. For example; + 6 = 56+ = 11
Step 2. Write the sum over the same denominator. 7 7 7 7

2. Subtraction of like fractions
Step 1. Subtract the numerators. For example; 8 − 2 = 82− = 6
Step 2. Write the difference over the same denominator. 15 15 15 15

ADDITION AND SUBTRACTION OF UNLIKE FRACTIONS
1. Addition of unlike fractions 2. Subtraction of unlike fractions
Step 1. Convert the given fractions to equivalent Step 1. Convert the given fractions to equivalent
like fractions. like fractions.
Step 2. Add the numerators. Step 2. Subtract the numerators.

Step 3. Write the sum over the same denominator. Step 3. Write the difference over the same denominator.

1
For example, Let's add and 13 . For example; Let's subtract 7 from 8 .
7 14 20 15
LCM of 7 and 14 is 14. LCM of 15 and 20 is 60.
14 ÷ 7 = 2 60 ÷ 15 = 4, 60 ÷ 20 = 3

2
So, 1 × = 2 So, 84× = 32 and 73× = 21
7 2 14 15 4× 60 20 3× 60
2 13 213+ 15 32 21 32 21− 11
+
Now, 14 14 = 14 = 14 Now, − = =
60 60 60 60

ADDITION AND SUBTRACTION OF MIXED FRACTIONS 1 2 16 58

1. Addition of mixed fractions For example; 5 + 8 = 3 + 7
3
7
Step 1. Change the mixed fractions to improper fractions. LCM of 3 and 7 is 21.
Step 2. Convert them into equivalent like fractions. 21 ÷ 3 = 7, 21 ÷ 7 = 3
Step 3. Add the numerators. 16 7× 112 58 3× 174
Step 4. Write the sum over the same denominator. So, 37× = 21 and 73× = 21

112 174 112 174+ 286 13
1 2 15 7 Now, + = = = 13
For example; 2 − 1 = − 21 21 21 21 21
7 5 7 5
LCM of 7 and 5 is 35.
2. Subtraction of mixed fractions
\ 35 ÷ 7 = 5 and 35 ÷ 5 = 7 Step 1. Convert the given fractions to improper fractions.
15 5× 75 77× 49
So, = and = Step 2. Convert them into equivalent like fractions.
75× 35 57× 35
75 49 75 49− 26 Step 3. Subtract the numerators.
Now, − = = Step 4. Write the difference over the same denominator.
35 35 35 35