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Stickers — Aiden's packet
Aiden had a packet of stickers. He gave half of them to his cousin. He then used 15 stickers to decorate his folder and had 45 stickers left. How many stickers did Aiden have at first?
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The pattern behind it: Working backwards
You know how it ended. Undo each step, last one first.
In this one. Work backwards: join the 15 stickers used to the 45 stickers left to rebuild the half Aiden kept, then double that half to rebuild the whole.
How to spot it
The question gives the final amount after a sequence of changes and asks what the amount was 'at first' or 'to begin with'.
Common mistake
Children undo the steps in the same order they happened rather than in reverse, or forget that a percentage profit is added to the cost price, so the final price is 120% of it, not 100%.
Try one like it
Standard Ivan and Helen — half his money Ivan gave half of his money to Helen. He then spent $18 and was left with $12. How much money did Ivan have at first?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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