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Mrs Lim's scarf — cut into eight triangles
Mrs Lim has a square scarf of side 21 cm. She cuts along the dotted lines to get one small square of area 9 cm² and 8 identical right-angled triangles. Triangle ABC is one such triangle. Find the length of AB.
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65 worked examples are free without a code, two from every pattern. No account, either way.
The pattern behind it: Seeing it move
Work out where the pieces land after a fold, cut or stack.
In this one. The same two legs give both a sum and a difference: their sum is the outer side of the scarf, while their difference is the side of the small square — so adding the two facts isolates one leg and subtracting isolates the other.
How to spot it
Words like 'folded', 'cut along the dotted line' or 'stacked' appear beside a shape, and the question asks for a length or angle that only makes sense once the pieces are in their new positions.
Common mistake
Children try to calculate the answer before working out where the pieces actually end up, skipping the visualisation step that the whole question depends on.
Try one like it
Challenging Canvas — cut into a square and eight triangles Ravi has a square piece of canvas of side 31 cm. He cuts along the dotted lines to get one small square of area 289 cm² and 8 iden…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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