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Maya and Liam had stickers in the ratio 7 : 5.
Maya and Liam had stickers in the ratio 7 : 5. After Maya gave 18 stickers to Liam, the ratio became 5 : 7. How many stickers did Maya have at first?
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The pattern behind it: Constant total
Money moves between two people, so their total never changes.
In this one. Giving stickers from Maya to Liam keeps their combined total unchanged, so the two equal 12-part totals make Maya's 2-part decrease exactly the 18 stickers transferred.
How to spot it
One person gives, sells or loses an amount to the other, and nobody outside the two people gains or loses anything.
Common mistake
Children draw different totals before and after, or forget that moving an amount from one person to the other changes the gap between them by twice that amount.
Try one like it
Standard Liam and Noah's cards — 7 : 5 becomes 5 : 7 The ratio of Liam's trading cards to Noah's trading cards was 7 : 5. After Liam gave some of his cards to Noah, the ratio became 5…The 33 problem patterns
All 33 patterns, one to a page — the 19 behind Primary 5 and 6 word problems, and the skills the younger years are built on. The bar model, how to spot it in the question, and the mistake children make. A booklet you can print. Free.
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