Percentages · Usually met around P6
Using percentages together
Whole × the %. Up 10% means × 110%.
How to do it
Method
Whole × the %. Up 10% means × 110%
50 up 10%: 50 × 110% = 55
Another way
Find the increase first
50 × 10% = 5, 50 + 5 = 55
In full
A percentage is a fraction out of 100. To find a percentage of an amount, multiply the whole by the percentage, then ÷ 100: 35% of a class of 40 → 40 × 35 = 1400, 1400 ÷ 100 = 14 pupils. To find what percentage one number is of another, do part ÷ whole × 100%: 14 out of 40 is 14 ÷ 40 × 100% = 35%. To increase by a percentage, multiply by (100% + the increase): 50 increased by 10% → 50 × 110% = 55. To decrease, multiply by (100% − the decrease): 50 decreased by 10% → 50 × 90% = 45. 20% off means you pay 80% of the price, and 25% off means you pay 75%: $200 with 20% off → 200 × 80% = $160. Or find the increase or decrease first, then add it or take it away: 50 × 10% = 5, 50 + 5 = 55.
Worked examples
Have a go first, then open each one for the answer and the working.
Example 1
$400, 25% off: $?
Show the answer and working
Answer: $400, 25% off: $300
25% off leaves 75% of the price: 400 × 75 = 30000, 30000 ÷ 100 = 300
Example 2
Orange: 25% of 60 trees = ?
Show the answer and working
Answer: Orange: 25% of 60 trees = 15
25% of 60: 60 × 25%, 60 × 25 = 1500, 1500 ÷ 100 = 15
Example 3
Read 72 of 180 pages = ?%
Show the answer and working
Answer: Read 72 of 180 pages = 40%
72 ÷ 180 × 100%: 72 × 100 = 7200, 7200 ÷ 180 = 40, so 40%
Practise it in the game →Percentages · Free to start, unlimited questions, no download