Page 81 - MAT KS3 Y8 Cambridge CheckPoint

7.7 Dividing an integer by a fraction

7.7 Dividing an integer by a fraction

To divide an integer by a fraction, turn the fraction upside Remember to cancel, if possible,
down then multiply by the integer. Then use the same before you do any calculations.
method that you have used previously.

Worked example 7.7

Work these out. a 12 ÷ 3 b 25 ÷ 10
8 13

a 12 × 8 Turn the fraction upside down and multiply.
3
12 ÷ 3 = 4 Work out 12 ÷ 3 mentally, as 3 will divide exactly into 12 to give 4.
4 × 8 = 32 Now multiply the 4 by 8 to give an answer of 32.
b 12 × 13 Turn the fraction upside down and multiply.
10
5 13 13
25 × You can divide 25 and 10 by 5, so cancel first. The question is now 5× .
10 2 2
5 × 13 = 65 You cannot cancel any further, so multiply the 5 by the 13.
1
65 ÷ 2 = 32 Finally work out 65 ÷ 2 and write the answer as a mixed number.
2
✦ Exercise 7.7

1 Work these out.
3
5
a 21÷ b 15÷ c 24÷ 6 d 18÷ 9 e 30÷ 10 f 20÷ 4
4 6 7 10 13 11
2 Work these out. Give each answer as a mixed number in its lowest terms.
In all parts, cancel before you do any calculations.
6
4
a 16 ÷ b 12÷ 8 c 22÷ d 34÷ 4 e 45÷ 18 f 21÷ 14
7 11 9 5 23 15
3 Which of these cards gives an answer that is different from the other two?
Show all your working. A B C

45÷ 5 51 ÷ 17 10 ÷ 2
8 25 15

4 This is part of Anders’s homework.
Use Anders’s method to work these out.
8
a 4 ÷ b 7 ÷ 14 10
9 19 Question Work out 5 ÷
c 3 ÷ 9 d 8 ÷ 24 17
11 29 10 17
1
A
A
A
A
A
A
Answer 5 ÷ = 5 ×
A
A
e 6 ÷ 18 f 9 ÷ 36 17 10 2
25 41 17
= 1 ×
2
17 ÷ 2 = 8 1
2
7 Fractions 79