Percentages Revision

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

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

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 60 + 21 = 81 Careful – add on to the correct number

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%

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