Percentage Change
OCR Module 8
Change?
• An Increase
• A Decrease
For example
• Increase £24 000 by 3%
3% of 24000
= 24000
x 103
= 24000
x 3
100
100
Total = £24 720
= =£720
£24 720
103% of 24000
MULTIPLIER of 1.03
For example
• Decrease £17.60 by 15%
Left with 85% of 17.60
85% of 17.60
MULTIPLIER of 0.85
= 17.60 x 0.85
= £14.96
What is the Multiplier for …
An INCREASE of
A DECREASE of
12%
1.12
12%
0.88
25%
1.25
25%
0.75
33%
1.33
33%
0.67
17.5%
1.175
17.5%
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%
110% of OLD = 38 500
OLD x 1.10 = 38 500
MULTIPLIER
= 1.10
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%
80% of OLD = 26.00
OLD x 0.80 = 26.00
OLD = 26.00 ÷ 0.80
OLD PRICE = £32.50
MULTIPLIER
= 0.80