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Mr Koh's stickers — animal and cartoon
Mr Koh had a collection of stickers. of them were animal stickers and the rest were cartoon stickers. After giving away 120 cartoon stickers and of the animal stickers, he had of the stickers left. How many stickers did Mr Koh give away?
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The pattern behind it: Branching
The second fraction is of one piece, not of the whole.
In this one. Rewrite "2/3 of the animal stickers were given away" as a fraction of the **whole collection** (1/5 left) — once every share is measured against the same whole, the 3/10 left and the 2/5 cartoon can be subtracted from one another, and the 120 lands on a known fraction of the whole.
How to spot it
A second fraction arrives after the first and is attached to a piece rather than to the whole — 'of the remainder', 'of what was left', or 'of the ones that were red'.
Common mistake
Children take the second fraction of the original total instead of the piece it was named against, which makes the amount come out too big.
Try one like it
Standard A dress and a handbag — Mei's savings Mei spent $48 on a dress. This was 3/8 of her savings. After buying the dress, she spent 1/5 of the remaining savings on a handbag…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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