Percentages

The word  percent means “out of one hundred”

%  means  ÷ 100   

Percentages are just fractions  with  a denominator of 100

Examples

1 2 3

As simplified fractions:

4

5

6

And as decimals:

9 8 7

Converting between percentages ,fractions and decimals

Calculating a score as a percentage

This is just the same as turning a fraction into a percentage.

Example

Fred attained 23 marks out of 40 for his test.

What was has score as a percentage ?

18

Sometimes it is easier just to calculate the equivalent fraction that gives a denominator of 100:

Examples

19 20

 

Calculating percentages – using fractions

Convert the percentage into  a fraction then follow the rules for  calculating fractions.

 

Example

Find 20% of £45

10

Calculating percentages – using decimals

Convert to a decimal, then multiply.

Example

Find 20% of £45

11

 

Calculating percentages –  using units

          to find 1% of a value – just divide by 100
            to find 10% of a value – just divide by 10
            to find 100% of a value – just divide by 1

 The required  percentage can then be built up.

Example

Find 20% of £45

12

 

Useful tips:

To find 5% , half 10%  or  multiply 1% by 5

Examples

13

14

 

 

Value Added Tax

VAT

 

VAT is currently at 20%, but used to be at 17.5%

To calculate VAT at 20 %, divide the value by 10 and double !

Examples

Calculate the VAT at 20% on an item costing £450.

15

 

A lawnmower costs £450 ex VAT.

What is the price inclusive of VAT ?

16

 

Vat @ 17.5% is very easy to calculate:

17.5% = 10% + 5% + 2.5%

so,

Example

Calculate the VAT due at 17.5% on an article costing £360.

17

VAT due is £63

 

Calculating percentages –  using the calculator

Save yourself effort – divide the number in front of the percentage sign by 100.

100%   = 1             

10 %  = 0.1

1% = 0.01 0.1% = 0.001

Examples

90% of £34,567 = 0.9 x 34,567 = £31,110.30

235.6% of £34,567 = 2.356 x 34,567 = £81439.85

© Alexander Forrest