top of page

Award in Mathematics -

Number and Measure (Level 1)

​

Topic 14: Calculating percentages 

Calculator
tick%25203_edited_edited.png

A percentage is a fraction that always has a denominator (bottom number) of 100. The symbol for 'percent' is %.

​

1% = 1/100  (1 equal part out of 100)

​

10% = 10/100 

​

50% = 50/100 

​

99% = 99/100 (99 out of 100)

​

100% = 100/100 

​

A good way to visualise percentages is to think of the battery level indicator for a mobile phone or tablet.

​

​

​

​

​

​

​

​

​

You will sometimes be asked to calculate a certain percentage of a given amount.

​

A good example is the amount of tax that must be paid on a bill. Here is an example.

​

       "An electric bill was £95 plus tax at 20%

       Work out the cost of the tax."

​

 

Remember that a percentage is like a fraction 'out of 100'. So 20% = 20/100.

​

So you can work out 20% of £95 like this:

£95 × 20 ÷ 100 = £19

​

​

A good rule to remember is,

​

"If you work out 1% of a number you can work out ANY percentage of it."

​

This means doing the '÷ 100' part of the calculation first, to find 1%.

​

For example, 

​

     50 ÷ 100 = 0.5, so 1% of 50 is 0.5

 

Now it is easy (with a calculator) to find any percentage of 50:

​

2% of 50 is 1                (0.5 × 2 = 1)

​

10% of 50 is 5              (0.5 × 10 = 5)

​

40% of 50 is 20            (0.5 × 40 = 20)

​

75% of 50 is 37.5         (0.5 × 75 = 37.5)

​

6.8% of 50 is 3.4          (0.5 × 6.8 = 3.4)

​

99.9% of 50 is 49.95    (0.5 × 99.9 = 49.95)

​

​

batteries.PNG
bottom of page