Page 86 - ICSE Math 5

Addition and Subtraction of Mixed Fractions

Mixed fractions can be added or subtracted in two different ways.

• By first converting them to improper fractions, then to like fractions and finally adding or
subtracting them.
• By adding or subtracting the whole numbers and fractions separately.

2 1
Example 20: Add 4 and 2 .
5 5 Mental Maths
2 1 Fill in the blanks.
Solution: 4 + 2 5 5
5 5 (a) 1 + ____ = 5
2 1 9 9
Step 1: Convert 4 and 2 to improper fractions. 1
5 5 (b) 2 + ____ = 2
2
4
2 (4 × 5) + 2 20 + 2 22 (c) ____ – 7 = 3 4
4 = = = 9 9
5 5 5 5
4
(d) 1 – = ____
1 (2 × 5) + 1 10 + 1 11 9
2 = = =
5 5 5 5
22 11
So, we have + .
5 5
Step 2: Add the numerators of the fraction since they are like fractions and keep
the denominator as it is.

22 11 22 + 11 33 3
5 + 5 = 5 = 5 = 6 5
2 1 3
So, 4 + 2 = 6 .
5 5 5
Alternatively,

2 1 2 1 3 3
4 + 2 = (4 + 2) + + = 6 + = 6
5 5 5 5 5 5
add the
whole add the
numbers fractions
2 1 3
So, 4 + 2 = 6 .
5 5 5
3 4
Example 21: Subtract 2 from 3 .
11 9
4 3
Solution: 3 – 2
9 11
4 3 3 9, 11
Convert 3 and 2 to improper fractions.
9 11 3 3, 11
4 (3 × 9) + 4 31 3 (2 × 11) + 3 25 11 1, 11
3 = = and 2 = =
9 9 9 11 11 11 1, 1
31 25
So, we have – .
9 11
L.C.M. of 9 and 11 = 3 × 3 × 11 = 99

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