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The average weight of 38 children in a class is 15 kg. If 4 children leave the class whose average weight is 40 kg and 2 students join the class whose average weight is 35 kg, then find the average weight of all the children in the class.

1. 55 kg
2. 40/3 kg
3. 43 kg
4. 41/9 kg

Correct answer: 40/3 kg

Solution

The initial total weight is 38 × 15 = 570 kg. After 4 children of average 40 kg leave, 160 kg is removed; after 2 students of average 35 kg join, 70 kg is added, giving 480 kg for 36 children. The new average is 480/36 = 40/3 kg.

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