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Percentage Change
OCR Module 8
Change?
• An Increase
• A Decrease
For example
• Increase £24 000 by 3%
3% of 24000
= 24000 x 3 100
= £720
Total = £24 720 103% of 24000
= 24000 x 103 100
= £24 720
MULTIPLIER of 1.03
For example
• Decrease £17.60 by 15%
85% of 17.60
= £14.96
Left with 85% of 17.60
= 17.60 x 0.85
MULTIPLIER of 0.85
What is the Multiplier for …
An INCREASE of
12%
25%
33%
17.5%
1.12
1.25
1.33
1.175
A DECREASE of
12%
25%
33%
17.5%
0.88
0.75
0.67
0.825
The Original Value?
• Often, we are given a price AFTER an increase or decrease
• To calculate this, we complete a REVERSE PERCENTAGE calculation
For example
After a 10% salary increase, David earned £38500
What was his salary BEFORE this increase?
NEW SALARY is the OLD SALARY plus 10%
MULTIPLIER= 1.10
110% of OLD = 38 500
OLD x 1.10 = 38 500
OLD = 38500 ÷ 1.10
OLD SALARY = £35 000
For example
A shirt was ON SALE for £26.00. It had been reduced by 20%. What was the original price?
SALE PRICE is the OLD PRICE less 20%
MULTIPLIER= 0.80
80% of OLD = 26.00
OLD x 0.80 = 26.00
OLD = 26.00 ÷ 0.80
OLD PRICE = £32.50
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