Maths Topic 13 - Percentages


Percentages – Conversion to Decimals, Using 10% and 1% for Calculations, Percentage Problems, Reserve % Problems. These maths skills are commonly tested in 11+ exams and Selective School exams in the UK.

Examples

Example Question 1:

What is 35% of 500?

Answer: 175

Explanation: 10% is 500 ÷ 10 = 50, so 30% will be 3 × 50 = 150. 5% of 500 will be exactly half of the 10% (50) = 25. Add together the 30% and 5% → 150 + 25 = 175

Example Question 2:

What is the full cost of an item if £1.90 = 40%?

Answer: £4.75

Explanation: 1% of the full amount of £1.90 (190pence) is 190p ÷ 40 = 4.75p, now multiply this by 100 to find the full 100% = £4.75

Example Question 3:

What is 150ml as a % of 1 litre?

Answer: 15%

Explanation: 150 over 1000 can be cancelled down to 15/100 = 15%

Video Tutorials

Conversion to Decimals Part 1

 

Conversion to Decimals Part 2

 

Using 10% and 1% for Calculations

 

Percentage Problems

Reverse % Problems