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Maths olympiad question · P2–P3★ Easy

Surplus and shortage: olympiad question 2

An easy question on surplus and shortage for P2–P3, with a step-by-step solution, diagrams and the answer. Surplus-and-shortage questions appear in the Hua Xia Cup's P1 to P5 papers; harder ones become questions about distance and time.

The question

Mum shares a bag of sweets equally among some children.

With 2 each there are 5 left over; with 3 each they are used up exactly.

How many children are there?

Show the hints (2)
  1. Hint 1: Going from 2 each to 3 each, how many more does each child get?
  2. Hint 2: The 5 left over are just enough for that.

Worked solution

Have a go first, then read the solution step by step.

  1. 1.With 2 each, 5 are left over.
  2. 2.With 3 each, every child gets 3 − 2 = 1 more, which uses up the 5 left over exactly.
  3. 3.The 5 left over, 1 a child, go round 5 ÷ 1 = 5 children.
  4. ⚠️Common mistake: 5 ÷ 3. The leftovers only pay for 1 more each.

Answer: 5 children

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