Today’s problem — free all day, every step. Every day has one.
Sticker book — trading and a bonus pack
Mei had some stickers in her sticker book. She traded with a friend, receiving 18 stickers and giving away 7 stickers. Then a bonus pack doubled the number of stickers in her book. She then had 60 stickers. How many stickers did she have before she traded with her friend?
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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 by undoing the latest operation first: halve to undo the doubling, then subtract the trade’s net gain.
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 Bus passengers — boarding, alighting, doubling There were some passengers on a bus. At the first stop, 12 passengers boarded and 5 got off. At the second stop, the number of pas…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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