Question P4 Rectangle and square measurement
A composite rectilinear figure is formed by removing a 4 cm by 3 cm corner from a 12 cm by 8 cm rectangle. Find its perimeter.
Answer
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Rectangle and square measurement
Use opposite equal sides, undo the area or perimeter formula, and count each outside edge once.
In this one. Trace only the outside boundary. The two new notch edges replace equal lengths removed from the original outer edges.
Squares tiling a rectangle, or a shape made of several rectangles joined together, point here. The question asks for area, perimeter, or the length of a missing side.
Children multiply length by width when the question actually asks for perimeter. On a composite shape, they add only the labelled sides and miss the ones they must work out themselves.
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