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Maths olympiad question · P4–P5★★ Medium

Sum and multiple: olympiad question 4

A medium question on sum and multiple for P4–P5, with a step-by-step solution, diagrams and the answer. Sum-and-multiple and difference-and-multiple questions appear in the Hua Xia Cup's P3 to P5 first rounds, qualifying rounds and finals.

The question

At Chinese New Year two sisters got $218 in red-packet money altogether.

The older sister got $38 more than twice what the younger got.

How much did the older sister get?

Show the hints (2)
  1. Hint 1: Without her extra $38, the older would have exactly twice as much. What would the total be then?
  2. Hint 2: Then the younger is 1 part and the older 2 parts.

Worked solution

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

  1. 1.Call the younger's money 1 part: the older has 2 parts plus $38. Together they have $218.
  2. 2.Take away the older's extra $38 and she has exactly 2 parts: 218 − 38 = 180.
  3. 3.That is 3 parts, so the younger has 180 ÷ 3 = $60.
  4. 4.The older has 218 − 60 = $158.
  5. ⚠️Common mistake: adding the $38. The older has $38 extra, so take it away first.

Answer: 158 dollars

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