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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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The pattern behind it: 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.
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.
Try one like it
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