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PSLE 2025 — Three rows of seats
There are 3 rows of seats in a classroom, each row with the same number of chairs. A group of students occupied of all the seats. Then, of the students left. The remaining students moved into the first 2 rows. What fraction of the seats in the first 2 rows are now occupied?
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The pattern behind it: Repeated identity
One length or count, described two ways in the same question.
In this one. The students did not change when they moved — only the seats they are counted against did: 4/5 × 5/8 = 1/2 of all the seats worth of students are now sitting in the 2/3 of the seats that the first two rows make up, and (1/2) ÷ (2/3) = 3/4.
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
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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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