Page 87 - ICSE Math 5

31 25
Convert and to equivalent fractions having the same denominator 99.
9 11
31 25 31 × 11 25 × 9 341 225 341 – 225 116 17
– = – = – = = = 1
9 11 9 × 11 11 × 9 99 99 99 99 99
4 3 17
So, 3 – 2 = 1 .
9 11 99
Alternatively,
4 3 4 3
3 – 2 = (3 – 2) + –
9 11 9 11
4 3
Since the L.C.M. of 9 and 11 is 99, convert and to equivalent fractions having
the same denominator 99. 9 11
4 × 11 3 × 9 44 27 44 – 27 17 17
1 + – = 1 + – = 1 + = 1 + = 1
9 × 11 11 × 9 99 99 99 99 99
4 3 17
So, 3 – 2 = 1 .
9 11 99

Exercise 6.2

1. Add the following fractions.
4 8 9 3 1 7 4 2
(a) + + (b) + + (c) 7 + 8
21 21 21 4 2 8 5 5
3 9 2 1 5 1 5 1
(d) 8 + 2 + 7 (e) 4 + 3 + 9 (f) 3 + 7 + 5
14 11 3 4 12 3 6 2

2. Subtract the following fractions.
54 26 19 10 11 20
(a) – (b) – (c) –
59 59 26 52 4 21
1 13 7 2 1
(d) 15 – 8 (e) – (f) 12 – 11
2 20 15 3 4

Multiplication of a Fraction by a Whole Number
1
Let’s multiply 3 and .
4
We know that multiplication is repeated addition.
1 1 1 1 1 + 1 + 1 3 3  1
Thus, 3 × = + + = = = .
4 4 4 4 4 4 4
Thus, to multiply a fraction by a whole number, we multiply the whole number by the numerator
of the fraction and keep the denominator as it is.
4 Remember
Example 22: Multiply 7 by .
5 While multiplying a fraction
4 7  4 28 by a whole number, always
Solution: 7 × = = (Improper fraction)
5 5 5 express your answer in the
3 lowest terms.
= 5 (Mixed fraction)
5
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