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P6 Repeated identity

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Aisha bought some hair clips and gave half of them to Priya.

Aisha bought some hair clips and gave half of them to Priya. Priya bought some bracelets and gave half of them to Aisha. Aisha lost 5 bracelets and Priya lost 6 hair clips. The ratio of Aisha's bracelets to hair clips becomes 1:4 and the ratio of Priya's bracelets to hair clips becomes 1:3. How many bracelets did Priya buy?

One step of the worked solution to Aisha bought some hair clips and gave half of them to Priya., drawn in pencil.
7 steps, drawn in pencil

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The pattern behind it: Repeated identity

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

In this one. Splitting each original collection in half and swapping makes both girls' holdings identical before the losses, so the same hair-clip amount can be written in two ways.

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.

Try one like it

Standard Water — poured into a second container 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 co…
All 19 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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