How_To_Be_Good_At_Math

66 NUMBERS •^ CALCULATING PERCENTAGES

Calculating percentages

We can find a percentage of any total amount, not just 100.

The total can be a number or a quantity, such as the area of

a shape. Sometimes we might also want to write one number

as a percentage of another number.

Answers on page 319

Working it out

Here are several shapes.

What percentage of each

shape has been shaded

a dark colour?

The whole amount of any shape

is 100%. To find the percentage

represented by one part, we divide

100 by the number of parts (10). This

gives us 10, so one tile equals 10%.

Take a look at this example.

There are 10 tiles altogether. What

percentage of the tiles have a pattern?

Finding a percentage

of a shape

On pages 64-65, we looked at

percentages using a square grid

divided into 100 parts. But what if

a shape has 10 parts or even 20?

100 ÷ 10 = 10

We multiply the result (10) by

the number of patterned tiles (6).

This gives us the answer 60. So, 60%

of the tiles have a pattern.

10 × 6 = 60

Each tile is

worth 10%

There are 10

equal parts

The total

number of tiles

60% have

a pattern

TRY IT OUT

066-067_Percentage_as_a_number.indd 66 29/02/2016 14:10