NUMBERS • CALCULATING PERCENTAGES 67
10% of 800
A percentage is
just another way of
writing a fraction.
Divide the total
amount by 100
300 ÷ 100 = 3
3 × 30 = 90
First, we need to find 1% of 300,
so we divide the 300 by 100.
Finding a percentage of a number
We can also use percentages to divide a number into parts. There’s
more than one way to do this, but one method is to start by finding 1%.
Next, we multiply the answer by
the percentage we need to find.
This gives us the answer:
30% of 300 is 90.
The 10% method
In the example above, we began by finding 1% of the
total. Sometimes, we can get to the answer more quickly
by first finding 10%. This is called the 10% method.
30% of 300 = 90
30% of 300 =?
6 × 35 = 210
350 ÷ 10 = 35
65% of £350 =?
We need to find 10% of £350,
so we divide the amount
by 10. This gives us 35.
In this example, we need
to work out 65% of £350.
We know that 10% is 35, so 60%
will be 6 groups of 35.
We’ve found 60% of 350. Now we just
need another 5% to get 65%. To work
out 5%, we simply halve the 10% amount.
Now add 60% and 5% to find
65%. So, 65% of £350 is £227.50.
210 + 17.50 = £227.50
35 ÷ 2 = 17.50
Let’s find 30% of 300.
10% of 550
10% of 200
10% challenge
Time yourself and see
how quickly you can
work out the following
percentages:
Answers on page 319
TRY IT OUT
066-067_Percentage_as_a_number.indd 67 29/02/2016 14:10