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Rectangle — a square bitten out of one corner
A rectangle has a length of 18 cm and a width of 9 cm. A square of side 4 cm is cut from one corner. Find the area of the remaining shape.
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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. Cutting a corner off takes exactly that piece away from the area — but nothing at all from the perimeter, because the two new edges are the same lengths as the two edges removed.
Also uses: Overlap and cancel
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
Standard Net of a cube — the opposite face The figure is the net of a cube. Which face is opposite face A when it is folded?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.
A PDF, and a note when new solutions go up.