Fractions And Percentages Worksheet Page 13
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28MEP Pupil Text 11
11.5 Percentage Increase and Decrease
Percentage increases are calculated using
actual increase
=
×
Percentage increase
100%
initial value
Similarly, percentage decreases are calculated using
actual decrease
=
×
Percentage decrease
100%
initial value
Worked Example 1
The population of a village increased from 234 to 275 during one year. Find the
percentage increase.
Solution
=
−
234 = 41
Actual increase
275
.
41
=
×
Percentage increase
100%
234
= 17 52
. %
(to 2 decimal places)
Worked Example 2
When a beaker of sand is dried in a hot oven its mass reduces from 450 grams to
320 grams. Find the percentage reduction in its mass.
Solution
=
−
Actual reduction
450
grams
320
grams
= 130
grams.
130
=
×
Percentage reduction
100%
450
= 28 9 . %
. %
Worked Example 3
John buys calculators for £5 each and then sells them to other students for £6.90.
Find his percentage profit.
Solution
=
−
Actual profit
£ .
6 90
£
5
= £ . 1 90
1 90
.
=
×
Percentage profit
100
%
5
= 38%
.
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