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Question P6 Factors and multiples

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PSLE 2024 — Two numbers six factors

Two numbers are each less than 40 and add up to 60. Each of them has exactly 6 factors. What are the two numbers?

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Answer

28 and 32.

About this method

Factors and multiples

The answer comes from how the numbers divide, not from a bar model.

In this one. The factor count comes from the powers in the prime factorisation — add one to each power and multiply — so 6 = 3 × 2 or 6 = 6 × 1 means the number can only be p² × q or p⁵, which turns a hunt over 39 numbers into a five-item list.

The most teams that divide evenly12 teamsteams12 divides 72 and 60One team6 girls, 5 boysgirls72 ÷ 12boys60 ÷ 12

How to spot it

Words like 'as many teams as possible', 'equally divided with none left over', or 'has exactly this many factors' appear, without any ratio or fraction in sight.

Common mistake

Children reach for the lowest common multiple when the question needs the highest common factor, or try to list every factor of a number by hand instead of building it from its prime factors.

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