1. Writing one quantity
as a percentage
of another

2. 82% Example 1 Consider a mark in a Maths test of
As this is a mark out of 100, it is easily written as a percentage
82%

3. Example 2
Consider a mark in a Science test of 35 out of 50
We can try and make it out of 100 2 70 35 50 =
100 2 35 50
Because we multiply 50 by 2 to get 100, we will do the same to the top number
This means
= 70%

4. Example 3
Express 52 out of 65 as a percentage
Sometimes it is not so easy to make the mark out of 100 as we did in the last example
Here we write the mark as a fraction 52 65
Now multiply by
100
to change to a
percentage
This gives us
the decimal
equivalent
52  65 = 08
08  100 = 80% 52 65
= 80%

5. Did you see what we did with the fraction? It would be a good idea to
top 
bottom 
100
It would be a good idea to
learn this off by heart

6. Example 4
Caroline’s phone contract increased from £24 per month to £28 per month. Find the percentage increase.
Here the increase is £4 on the original cost of £24.
We write this as a fraction. 4 24
Use your
calculator
Calculation: = 4  24  100
= 16 …%
= 167% to 1 decimal place

7. Answer to the nearest whole number
Calculate the percentage when pupils score
27 out of 35 b) 73 out of 90
Answer to the nearest whole number
An item is bought for £72 and sold for £110. What was the percentage profit?
An item is bought for £185 and sold for £110. What was the percentage loss?