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Question P6 Constant part

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Ali and Ben's savings — the ratio shifts

The ratio of Ali's savings to Ben's savings was 3 : 5. After Ali saved another $24, the ratio became 9 : 10. How much did Ali have at first?

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About this method

Constant part

The ratio changes, but one person's amount stays the same.

In this one. Ben's money never moves, so make Ben's share the same number of parts in both ratios — 3 : 5 = 6 : 10 against 9 : 10 — and the $24 is the 3-part gap that is left.

BeforeAliBenAfterAli never changesAlisame as beforeBengained 2

How to spot it

A ratio changes and the question tells you only one person gained or lost an amount, while the other kept what they had.

Common mistake

Children keep the same number of shares for the person whose amount did not change. The amount stays the same, but the size of a share can differ between the two ratios.

Practise a similar question

Challenging A farm had 150 more chickens than ducks. After 90 ducks were sold at the market, the ratio of the number of ducks to the number of chickens was 1 : 4. How many chickens were there?
All 8 with this pattern →
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