Page 81 - Revised Maths Wisdom Class - 6

Fractions 79

4 11 7 2
For example, let us add and . Now let us subtract and .
7 7 9 9
4 11 ( 411+ ) 15 7 2 72− 5
+ = = − = =
7 7 7 7 9 9 9 9

Adding/Subtracting Unlike Fractions

To add or subtract two unlike fractions, we follow these steps:
Step 1: Find the LCM of the denominators.
Step 2: Convert each unlike fraction into like fraction by making the LCM of step 1 as their common denominator.

Step 3: Add/subtract the like fractions.
5 4 3 1
For example, let us add and Now, let us subtract and
6 15 4 10
LCM of 6 and 15 is 30 LCM of 4 and 10 is 20
55× 25 42× 8 35× 15 12× 2
⇒ = and = ⇒ = and =
65× 30 15 2× 30 45× 20 10 2× 20
5 4 25 8 25 8+ 3 1 15 2
+ = + = − = −
6 15 30 30 30 4 10 20 20

= 33 = 1 3 = 15 2- = 13
30 30 20 20

Adding/Subtracting Mixed Fractions
To add or subtract mixed fractions, any one of the following methods may be used:
Method 1: Write them as improper fractions and then add or subtract.

2 1 1 1
For example, let us add 1 and 1 10 Now let us subtract 2 from 3
5
We write them as improper fractions, 16 7 3 5
7 11 i.e., −
i.e., and 5 3
5 10 LCM of 3 and 5 is 15

LCM of 5 and 10 is 10 75× 35 16 3× 48
72× 14 11 1× 11 ⇒ = and =
⇒ = and = . 35× 15 53× 15
52× 10 10 1 10×
16 − 7 = 48 − 35 = 48 35− = 13 .
7 11 14 11 25 5 1
⇒ 2 5 3 15 15 15 15
5 10 10 10 10 2 2

Method 2: Add/Subtract the whole parts separately and the fractional parts separately. Write the result as mixed
fraction or improper fraction.
1 1
For example, let us add 1 and 2
2 3
We add the whole parts, i.e., 1 + 2 = 3