Brainlag PlusShare an amount in a ratio, work from one share or the difference between shares, combine two ratios, and (Higher) solve problems where a ratio changes.
Find one part first
To share £72 in the ratio 3 : 5, count the parts, find one part, then multiply.
- 3 + 5 = 8 parts
- one part = £72 ÷ 8 = £9
- first share = 3 × £9 = £27
- second share = 5 × £9 = £45
- check: £27 + £45 = £72
The same idea works backwards. If the ratio is 3 : 5 and the first share is £27, then 3 parts = £27, so one part is £9. If instead the second gets £18 more than the first, the difference is 5 − 3 = 2 parts, so one part is £18 ÷ 2 = £9. The £18 is two parts, not one: that is the usual slip.
The rest of this lesson and its 8 practice questions are in Plus.
Screen 1 of 4, free to read.
- 8 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards