Multiple choice

The average weight of a group of eight people increased by 2.5 kg when a person weighing 80 kg joined in place of one of the members of the group. The weight of the member replaced was:

  1. 60 kg

  2. 77.5 kg

  3. 70 kg

  4. 62.5 kg
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A Correct answer
Explanation

Let the original sum of weights be S. New sum = S - replaced + 80. Increase = 2.5 * 8 = 20. So, 80 - replaced = 20. Replaced = 60 kg.

AI explanation

The total increase in the group's weight is 8 people multiplied by the 2.5 kg increase in the average, which equals 20 kg. This means the new person weighs 20 kg more than the person they replaced. Since the new person weighs 80 kg, the replaced member weighed 80 kg minus 20 kg, resulting in a weight of 60 kg.

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