Chapter 16 Ratio And Proportion Worksheet - Bbc Active Page 3
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1116.2 Solving ratio problems
D
In a cinema, there are 160 children and 200 adults.
3
a
What fraction of the audience are children?
Write down the ratio of the number of children to the number of adults.
b
Give your ratio in its simplest form.
Write your answer to part
in the form 1 : n.
c
b
The length of a model aeroplane is 16 cm. The length of the real aeroplane is 60 m.
4
Work out the ratio of the length of the model aeroplane to the length of the real aeroplane.
Write your answer in the form 1 : n.
Write these ratios in the form 1 : n.
5
_
1
3 hours :
hour
£2 : 40p
2 m : 4 cm
25 g : 1 kg
a
b
c
d
2
16.2
Solving ratio problems
Objective
Why do this?
You can solve problems using
A teacher taking some pupils on a school trip knows that the ratio of
ratio.
staff to students must be 1 : 15. Once the number of pupils on the trip
is known, the number of staff needed can be calculated.
Get Ready
1. Write the ratio in its simplest form.
a 10 : 15
b 130 : 650
c 4 cm : 35 mm
d 45 g : 1 kg
Key Point
If the ratio of two quantities is given and one of the quantities is known, then the other quantity can be found.
This can be done using equivalent ratios.
Example 2
To make concrete, 2 parts of cement is used to every 5 parts of sand.
a
Write down the ratio of cement to sand.
b
4 buckets of cement are used. How many buckets of sand will be needed?
c
20 buckets of sand are used. How many buckets of cement will be needed?
2 : 5
a
4 2 2
b
The amount of cement has been multiplied by 2.
cement
:
sand
2
:
5
�2
�2
Multiply 5 by 2.
4
:
10
10 buckets of sand will be needed.
equivalent ratios
265
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