Multiple choice

The average weight of a group of 20 boys is 46 kg. If a boy A leaves the group, the average weight increases by 1 kg. If a new boy B joins the group, the average weight decreases by 1 kg. What is the sum of the weights of A and B?

  1. 52 kg

  2. 67 kg

  3. 43 kg

  4. 59 kg
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A Correct answer
AI explanation

The total weight of the 20 boys is 20 times 46, giving 920 kg. When boy A leaves, the total weight of the remaining 19 boys is 19 times 47, which equals 893 kg, making boy A's weight 27 kg. When boy B joins the original group, the total weight for 21 boys becomes 21 times 45, yielding 945 kg, so boy B weighs 25 kg. The sum of the weights of A and B is 27 plus 25, resulting in 52 kg.

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