Academic Skills Advice
Percentages Refresher Sheet 2
Finding a percentage of a number
If you are asked to find 25%, 50%, 75% or any multiple of 5% you can use the easy
method described in Refresher Sheet 1. However the following method will work for
finding any percent:
𝑝𝑒𝑟𝑐𝑒𝑛𝑡
100
×
𝑎𝑚𝑜𝑢𝑛𝑡
1
Examples:

Find 42% of £350
42
100
×
350
1
= £147 (if you need to do this without a calculator you need to know
how to multiply fractions: see fractions 3)

Find 28% of £242
28
100
×
242
1
= £67.76
Percentage Increase or Decrease
Find the percent as above then:
Add it on for an increase
Subtract it for a decrease
Examples:

The price of a book increases by 12%. If the original price is £4.70 what is the new
price?
12
100

×
470
1
= 56.4𝑝 so the new price is £4.70 + 56p = £5.26
The value of a car decreases by 34%. If the original price was £8950 what is it worth
now?
34
100
×
8950
1
= £3043 so the new price is £8950 - £3043 = £5907
1
H Jackson 2008 / Academic Skills
Except where otherwise noted, this work is licensed under
http://creativecommons.org/licenses/by-nc-sa/3.0/
Practice Questions:
Find the following using the easy 10% method (See Percentages 1):
50% of 320
25% of 484
5% of 24
20% of 350
15% of 420
30% of 232
Find the following:
14% of 8 hours
23% of 190cm
6% of £305
9% of £224
12% of 222
18.5% of £34
7.2% of 24kg
72.5% of £4200
8.95% of £63
24.2% of 284m
Increase each of the following by the given percentage.
£84 by 30%
£250 by 20%
340g by 6%
14kg by 5%
820m by 55%
Decrease each of the following by the given percentage.
820cm by 50%
24m by 25%
45kg by 16%
82g by 11%
180 minutes by 15%
Answer the following:
A car is originally valued at £9650. If it decreases by 15% what is it’s new value?
Mary’s salary was £34,500. She received a 4% increase, what is her new salary?
An advertising company has to reduce it’s workforce by 12%. If there are 400 employees,
how many will remain after the redundancies?
H Jackson 2008 / Academic Skills
2