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P4 Rectangle and square measurement

find a rectangle side from area

A rectangle has area 63 cm² and length 9 cm. Find its width.

A rectangle with one unknown dimension; drawing is not to scale.9 cm?
One step of the worked solution to find a rectangle side from area, drawn in pencil.
5 steps, drawn in pencil

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The pattern behind it: Rectangle and square measurement

Use opposite equal sides, undo the area or perimeter formula, and count each outside edge once.

In this one. Area is arranged in equal rows. Dividing by one dimension gives the number of rows in the other direction.

Undo or tracearea48 split into rows of 8 gives width 6perimeterfour equal square sides

How to spot it

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.

Common mistake

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.

Try one like it

Standard find a rectangle side from area A rectangle has area 60 cm² and length 12 cm. Find its width.
All 11 with this pattern →

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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