Chapter 16 Ratio And Proportion Worksheet - Bbc Active Page 2
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11Chapter 16 Ratio and proportion
16.1
Introducing ratio
Objectives
Why do this?
You can simplify ratios.
Maps use ratio so that the actual distance between
two places can be worked out by measuring the
You can write down a fraction from a ratio.
You can write ratios in the unitary form.
distance on the map and then using the ratio.
Get Ready
1. The scale on a road map is 1 : 200 000.
Sunderland and Newcastle are 9 cm apart on the map.
Work out the real distance, in km, between Sunderland and Newcastle.
Key Points
Ratios are used to compare quantities.
The simplest form of a ratio has whole numbers with no common factor.
Ratios are sometimes given in the form 1 : n where n is a number.
This is called the unitary form of a ratio.
It is most often used for scales in maps and scale drawings (see Section 12.6).
To write a ratio in the form 1 : n, divide each number in the ratio by the fi rst number in the ratio.
_
_
5
8
For example, 5 : 8
:
5
5
1 : 1.6
Example 1
In a library, there are 560 fi ction books and 420 non-fi ction books.
a
Write down the ratio of the number of fi ction books to the number of non-fi ction books.
Give your ratio in its simplest form.
b
Give your ratio in the form 1 : n.
a
560 : 420
Write down the ratio. The number of fi ction books goes fi rst.
Divide both numbers by 10.
56 : 42
Divide both numbers by 14.
4 : 3
4 : 3 is the simplest form.
__
3
b
4 : 3 1 :
n .
Divide both numbers by 4 to give the ratio in the form 1 :
4
(or 1 : 0.75)
Questions in this chapter are targeted at the grades indicated.
Exercise 16A
D
Write each ratio in the form 1 : n.
1
a
5 : 15
b
8 : 32
c
4 : 14
d
6 : 3
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1
3
2
30 : 9
15 : 9
: 4
:
e
f
g
h
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8
10
In a school, there are 120 computers. There are 600 students in the school.
2
Advise the Headteacher of the ratio of the number of computers to the number of students.
Give your ratio in the form 1 : n.
264
ratios
unitary
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