Page 85 - Start Up Mathematics_5

3 1
Example 11: Multiply 1 by 2 .
5 2
3 1 (1 × 5) + 3 (2 × 2) + 1
Solution: 1 × 2 = ×
5 2 5 2
4 1
4
= (5 + 3) × (4 + 1) = 8 × 5 = 4 × 1 = = 4
5 2 5 2 1 × 1 1
1 6 1 1
Example 12: Multiply 3 by .
4 11 Maths Fun
1 6 (3 × 4) + 1 6
Solution: 3 × = × Archana’s mother baked 7 pastries.
4 11 4 11 She gave half of what she made plus
3
(12 + 1) 6 13 6 a pastry to her friend Payal. She then
= × = ×
4 11 4 11 gave half of what was left plus half
2 a pastry to another friend Sonam.
13 × 3 39 17 Then, she kept what was left for
= = = 1
2 × 11 22 22 Archana. How many pastries
did each person get?
Properties of multiplication of fractions

3 4 4 3
1. Two fractions can be multiplied in any order. For example, × = ×
7 5 5 7
2. Three fractions can be multiplied by grouping them in any order.
2 1 4 2 1 4
For example, × × = × ×
3 9 7 3 9 7
8 8
3. A fraction when multiplied by zero results in zero. For example, × 0 = 0 × = 0
13 13
4. A fraction when multiplied by 1 gives the same fraction.

3 3 3
For example, × 1 = 1 × =
5 5 5

EXERCISE 5.2

1. Find the product.

4 3 2 4 3 6 5 12 11 8
(a) × (b) × (c) × (d) × (e) ×
9 8 3 5 7 11 9 15 12 13
9 2 11 5 6 6 32 7 9
(f) × (g) × (h) × 3 (i) × (j) ×
16 7 15 22 21 24 18 36 28
2. Multiply the following fractions.

2 2 5 5 3 1 2 7 8 3
(a) × × (b) × × × (c) × ×
4 7 9 12 7 6 3 9 11 4

6 26 5 11 30 6 4 8 8 5
(d) 13 × 42 × 9 (e) 15 × 33 × × 30 (f) 14 × 16 × 9
7

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