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Question P6 Repeated identity

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Nine tiles — the area of WXYZ

9 identical rectangular tiles are used to make a mosaic panel WXYZ for a bathroom wall. 4 tiles are laid flat along the top and 5 tiles are stood upright below them, as shown. The perimeter of WXYZ is 174 cm. Find the area of WXYZ.

9 identical tiles forming rectangle WXYZ: 4 lying flat across the top and 5 standing upright below, drawn to scale.WXYZ

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About this method

Repeated identity

One length or count, described two ways in the same question.

In this one. The edge WX is the same length read two ways — as 4 tile-lengths and as 5 tile-breadths — so 4L = 5B, and that one equation fixes the ratio L : B = 5 : 4 before any number is used.

the same edge, measured twicelong tilesshort tilesboth rows end level, so 3 long = 5 short

How to spot it

A shape or count is described from two viewpoints in the same question, such as one edge measured as a number of long pieces and again as a number of short pieces.

Common mistake

Children treat the two descriptions as separate quantities and add them. Both describe the same quantity, so the two must be equal.

Practise a similar question

Standard A rectangular tank measures 30 cm by 20 cm by 25 cm. It is 3/5 full of water. All the water is poured into a second rectangular container with a base area of 200 cm². What is the height of the water in the second contain…
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