Question

The average weight of a group of 20 boys was calculated to be 89.4 kg and it was later found that one weight was misread as 78 kg instead of 87 kg. The correct average weight is:
1. 89.55 kg
2. 89.25 kg
3. 89.85 kg
4. 88.95 kg

Answer 1

Correct Answer - Option 3 : 89.85 kg

Given:

Average of 20 boys = 89.4 kg

Misread 78 kg instead of 87 kg

Formula used:

Average = Sum of all observations/Total number of observations

Calculation:

Sum of all observations = 89.4 × 20 = 1788

Correct sum of observations = 1788 – 78 + 87 = 1797

Correct average = Correct sum/20 = 1797/20 = 89.85

∴ The correct average is 89.85 kg