year 8 maths

310 Chapter 5 Ratios and rates
PROBLEM-SOLVING AND REASONING
9, 10, 13 10–15
10–12, 14–17
9 What is the cost of paving a driveway that is 18 m long and 4 m wide, if the paving costs $35 per
square metre?
10 A saltwater swimming pool requires 2 kg of salt to be added for every 10 000 litres of water. Joan’s
swimming pool is 1.5 metres deep, 5 metres wide and 15 metres long. How much salt will she
need to add to her pool?
11 The Bionic Woman gives Batman a 12 second start in a 2 kilometre race. If the Bionic Woman runs
at 5 km/min, and Batman runs at 3 km /min, who will win the race and by how many seconds?
Example 19
12 At a school camp there is enough food for 150 students for five days.
a How long would the food last if there were only 100 students?
b If the food ran out after only four days, how many students attended the camp?
13 Michelle can complete a landscaping job in six days and Danielle can complete the same job in
four days. Working together, in how many days could they complete the job?
14 Three bricklayers, Maric, Hugh and Ethan, are cladding a new home. If Maric works alone, the job
would take him eight days to complete. If Hugh works alone, the job would take him six days to
complete, and if Ethan works by himself, the job would take him 12 days to complete.
a If the three men work together, how long will it take them to complete the job?
b What fraction of the house will each bricklayer complete?
15 Four cans of dog food will feed three dogs for one day.
a How many cans are needed to feed 10 dogs for six days?
b How many dogs can be fed for nine days from 60 cans?
c For how many days will 40 cans feed two dogs?
16 If it takes four workers, 4 hours to dig four holes, how long would it take two workers to dig six holes?
17 State the units required for the answer to each of the following rate calculations.
a $205/kg × 48 kg
b 62 s × 12 m/s
c 500 beats ÷ 65 beats/min (bpm)
d 4000 revolutions ÷ 120 rev/min
Cambridge Maths NSW
Stage 4 Year 8 Second edition
ISBN 978-1-108-46627-1 © Palmer et al. 2018
Cambridge University Press
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