Question P6 Seeing it move
Today’s problem — free all day, every step. Every day has one.
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.
Answer
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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.
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.
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.
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