year 8 maths

334 Chapter 5 Ratios and rates
6 Divide:
a $80 in the ratio 7 : 9 b 200 kg in the ratio 4 : 1 c 40 m in the ratio 6 : 2
d $1445 in the ratio 4 : 7 : 6 e $1 in the ratio 3 : 1 : 1
7 a The ratio of the cost price of a TV to its retail price is 5 : 12 . If its cost price is $480 , calculate its
retail price.
b The ratio of Taylah’s height to Ben’s height is 12 : 17 . If the difference in their heights is 60 cm ,
how tall is Taylah?
c Orange juice, pineapple juice and guava juice are mixed in the ratio 4 : 3 : 2 . If 250 mL of guava
juice is used, how many litres of drink does this make?
8 Express each rate in simplest form.
a 10 km in 2 hours b $650 for 13 hours c 2800 km in 20 days
9 Copy and complete.
a 400 km on 32 litres = km/L
= L/100 Km
c
1
$1200 in day =
2
$/day
= $/h
b 5 grams in 2 min = g/min
= g/h
10 For a scale of 1 : 1000 , find the real length (in metres) if the scale length is given as:
a 0.0002 m b 2.7 cm c 140 mm
11 Two cities are 50 km apart. How many millimetres apart are they on a map that has a scale of
1 : 100 000?
12 Find the scale factor for the following pairs of similar figures, and find the value of x.
a 4 cm
b
3 cm
5 cm
9 cm
4 cm
6 cm x cm
15 cm
x cm
6 cm
13 Copy and complete.
a $120/h = _____ c/min b 6 m/s = _____ km/h c 720 km/h = _____ m/s
14 a A truck uses 12 litres of petrol to travel 86 km . How far will it travel on 42 litres of petrol?
b Samira earns $267.20 for a 12 -hour shift. How much will she earn for a 7 -hour shift?
c Tap 1 fills the pool in 12 hours, while tap 2 fills the same pool in 15 hours. How long does it take
to fill this pool if both taps are used?
15 a Sandra drives to her mother’s house. It takes 45 minutes. Calculate Sandra’s average speed if her
mother lives 48 km away.
b How long does it take Ari to drive 180 km along the freeway to work if he manages to average
100 km/h for the trip?
c How far does Tarik ride his bike if he rides at 4.5 km/h for 90 minutes?
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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