Page 70 - Cambridge+Checkpoint+Mathematics+Coursebook+9

7.3 Multiplying fractions

T
ia
s ho
’
f
t o
M
his is par
me
o
r
k.
4 This is part of Mia’s homework.
w
Use Mia’s method to work out
these multiplications. Write each
these multiplications. Write each Question Work out 2 1 × 2 4
answer as a mixed number in its
answer as a mixed number in its 2 15
simplest form. Answer c Change to improper fractions: 5 × 34
2 15
1
3
a 1 × 3 b 2 1 × 3 2 d Cancel common factors: 1 5 × 34 17
2 5 4 3 1 2 15 3
1
2
1
c 1 × 3 d 3 × 1 5 e Multiply: 1 × 17 = 17
8 6 3 22 1 3 3
3 3 4 5 f Change to a mixed number: 17 = 5 2
e 3 × 4 f 4 × 2 3 3
4 5 7 16
g 8 2 × 5 h 3 × 6 4
9 37 5 11
5 Read what Xavier says.
If I multiply a fraction by itself, my answer will
always be smaller than the fraction I started with.

Use at least two counter-examples to show that this statement is not true.
6 This is part of Razi’s homework.
2

Question I eat 1 of a pizza. My brother eats of what is left.
4 3
What fraction of the pizza does my brother eat?
Answer
Answer 3 is left, 3 × 2 = 1 3 × 2 1
Answer
4 4 3 4 3
2 1
= 1 × 1
2 1
= 1
2
Check 3 2 = 6 1 = 1 9
×
4 3 12 2 2

Razi works out the answer to the question by cancelling common factors before multiplying.
He checks his answer is correct by cancelling common factors after multiplying.
Use Razi’s method to work out and check the answer to these questions.
1
5
a The guests at a party eat of a cake. Sam eats of what is left. What fraction of the cake does
4
8
Sam eat?
5
7
b The guests at a party eat of the rolls. Ed eats of what is left. What fraction of the rolls
10
6
does Ed eat?
7 Fractions 69