Question

The average weight of a group of 20 boys was calculated to be 65 kg and it was later discovered that the weight of a boy was misread as 76 kg instead of the correct weight 66 kg. The correct average weight was:
1. 66 kg
2. 63 kg
3. 65.5 kg
4. 64.5 kg

Answer 1

Correct Answer - Option 4 : 64.5 kg

Given:

Incorrect average weight of 20 boys = 65 kg 

Formula used:

Average weight = Sum of the weights/Number of persons 

Correct average = (Sum of the weights - Wrong Entry + Correct Entry)/ Number of persons 

Calculation:

Correct average weight = (20 × 65 - 76 + 66)/20 

⇒ 1290/20 

⇒ 64.5 kg 

∴ The required result = 64.5 kg