Coins — Helen and Ivan
Helen and Ivan have the same total number of coins
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The pattern behind it: Repeated identity
One length or count, described two ways in the same question.
In this one. When two collections have the same total count, subtract them: everything matching cancels and only the 40 swapped coins are left to compare — so you never need a total you cannot find.
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
Challenging Priya and Wei Jie's beads — glass and plastic Priya and Wei Jie make bracelets, and each of them has the same total number of beads in his or her box: 200 beads, made up only o…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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