Ria says: I am thinking of a shape that has 4 sides. Sam may ask questions to work out exactly which shape it is. Which of these questions would be LEAST useful to Sam?
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Answer: Does it have 4 sides?
A useful question is one whose answer could still go either way. Ria has already said the shape has 4 sides, so asking that again is certain to get yes and rules nothing out. The other questions all split the four-sided shapes into two groups.
Why a child picks Are all 4 of its sides the same length?: This one helps: a square and a rhombus say yes, a rectangle and a kite say no.
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