1. Percentages Revision

2. Finding a percentage without a calculator
Rule
Always find 10% first by dividing by 10 and then you can work out other key percentages
Example
Find 35% of 400
10% = 40
30% = 120 5% = 20
So 35% = 140

3. Finding a percentage with a calculator
Rule
Divide by 100 and then multiply
Example
Find 28% of 96
28 ÷ 100 = 0.28
0.28 x 96 = 26.88

4. Increase / Decrease by a percentage
Rule
Find the percentage first
Then add on or take away
Example
Increase 60 by 35%
Find 35% of 60 = 0.35 x 60 = 21
= 81
Careful – add on to the correct number

5. Writing a quantity as a percentage
Rule
Divide the two numbers
Multiply by 100
Example
John scores 56 out of 80 on a test
56 ÷ 80 = 0.7
0.7 x 100 = 70%

6. Working out the percentage increase
Rule
Work out the actual increase
Divide by the original number and times by 100
Example
A baby increases in weight from 5kg to 6kg.
Actual increase = 1kg
1÷5 = 0.2
0.2 x 100 = 20% increase