Percentages

Percent means "per hundred" or "out of one hundred".

So if we say that "20 percent of the children in a school have blue eyes", we mean that if we took 100 children from the school and looked at their eyes, 20 would be blue. If we took 200 children from the school and looked at their eyes, then 20 out of every hundred would be blue, therefore 40 would be blue.

 We use a special symbol '%' to represent percent.

A good way of introducing percentages is to visualise them by using a 100 square and to colour in the percentages.

This square has 50 out of 100 squares coloured in red.

50 out of 100 is 50 percent ... 50% are red

note that 50 out of 100 are not coloured in

50 out of 100 is 50 percent ... 50% are not coloured

 

 

This square also has 50 out of 100 square coloured in red.

50 out of 100 is 50 percent ... 50% are red

It also has 25 out of 100 squares coloured in blue

25 out of 100 is 25 percent ... 25% are blue

note that 50 out of 100 are not coloured in

25 out of 100 is 25 percent ... 25% are not coloured

 

 

This square also has 50 out of 100 square coloured in red.

50 out of 100 is 50 percent ... 50% are red

It also has 25 out of 100 squares coloured in blue

25 out of 100 is 25 percent ... 25% are blue

10 out of 100 are green ... 10% are green

15 out of 100 are yellow ... 15% are yellow

Percent

 

Percent

 

 

Percent

Primary Resources have an excellent powerpoint resource - Percentages, Fractions of 100,
that is worth working through with your child. As is this Percentage Squares worksheet.

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To find the percentage of a number we divide the total amount by 100 - this will tell us what 1% of the total is, and then multiply by the amount that we wish to know.

To find 10% of 100, divide 100 by 100 = 1, then 10 x 1 = 10 ... 10% of 100 is 10

To find 10% of 50, divide 50 by 100 = 0.5, then 10 x 0.5 = 5 ... 10% of 50 is 5
(remember that to divide by 100, shift the number 2 places to the right)

To find 15% of 300, divide 300 by 100 = 3, then 15 x 3 = 45 ... 15% of 300 is 45

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Another method of finding the percentage of a number is to change the percentage required into a decimal and the multiply the number by it.

30% means 30 out of 10, which is a fraction 30/100 - to convert fractions to decimals, we divide the numerator by the denominator - 30 ÷ 100 = 0.3.

So 30% is the same as 30/100 which is the same as 0.3

To find the percentage of a number we can multiply by the equivalent decimal.

To find 10% of 100, decimal equivalent of 10% is 10 ÷ 100 = 0.1, 100 x 0.1 = 10
(remember that to multiply by 100, shift the number 2 places to the left)

To find 10% of 50, decimal equivalent of 10% is 10 ÷ 100 = 0.1, 50 x 0.1 = 5

To find 15% of 300, decimal equivalent of 15% is 15 ÷ 100 = 0.15, 300 x 0.15 = 45

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Some percentages are worth remembering

50% means a half

25 % means a quarter

75 % means three quarters

10 % means one tenth

 

Try these worksheets from Primary Resources:      Percentages 1      Percentages 2

 














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