Page 140 - Cambridge+Checkpoint+Mathematics+Coursebook+9

14.2 Solving problems

2 Lian delivers leaflets. She is paid $12 for delivering 400 leaflets.
How much is she paid for delivering: a 200 leaflets b 600 leaflets c 150 leaflets?

3 Six packets of biscuits cost $11.40.
a How much do 15 packets of biscuits cost? b How much do 7 packets of biscuits cost?
4 A shop sells apple juice in cartons of two sizes.
A 500 ml carton costs $1.30.
a Work out the cost of 250 ml of this apple juice.
A 750 ml carton costs $1.86. 500 ml 750 ml
b Work out the cost of 250 ml of this apple juice. $1.30 $1.86
c Which carton is better value for money?

5 This is part of Oditi’s homework.
She used inverse operations Question A pack of 60 food bags costs $5.40.
to check each calculation. A pack of 50 food bags costs $4.25.
Use Oditi’s method to check your Which pack is better value for money?
answers to these questions. Show
Answer
Answer
all your working. Answer 5.40 ÷ 6 = $0.90 for 10 bags.
a A box of 150 paper towels Check: 6 × 0.90 = $5.40
costs $2.70. 4.25 ÷ 5 = $0.85 for 10 bags.
A box of 250 paper towels Check: 5 × 0.85 = $4.25
costs $4.75.
Which box gives you better The pack of 50 bags is better value for
money.
value for money?
b A 400 g pack of cheese costs
$3.20. A 350 g pack of cheese costs $2.87.
Which pack is better value for money?

6 Carlos travelled between the UK and Spain when the exchange rate
was £1 = €1.18.
a When he went to Spain he changed £325 into euros (€).
How many euros did he get?
b When he went back to the UK he changed €80 into British pounds (£).
How many pounds did he get? Give your answer to the nearest pound.

7 When Adriana travelled to America the exchange rate was €1 = $1.31,
Adriana saw a camera in a shop for $449.
The same camera cost €359 in Madrid.
Where should Adriana buy the camera? Show your working and check your answer.

Summary

You should now know that: You should be able to:
+ The best way to compare ratios is to write each + Compare two ratios.
ratio in the form 1 : n, where n is a number. Then + Interpret and use ratios in a range of contexts.
you can compare the ratios by comparing the
values of n. + Recognise when two quantities are directly
proportional.
+ Two quantities are in direct proportion when their Solve problems involving proportionality.
ratios stay the same as they increase or decrease. +

14 Ratio and proportion 139