Question

The average height of 35 students was calculated to be 160 cm. It was detected later that one value of 170 cm was wrongly copied as 135 cm for the computation of the average. Find the correct average.
1. 158 cm
2. 161 cm
3. 156 cm
4. 164 cm
5. None of these

Answer 1

Correct Answer - Option 2 : 161 cm

Given:

Average height of 35 student = 160 cm

Wrongly copied height = 135 cm

Correct height = 170 cm

calculation:

Incorrect sum of the heights of 35 student = (160× 35) cm = 5600 cm

So, correct sum of the heights of 35 students = (incorrect sum) - (wrongly copied item) + (actual item) = (5600 - 135 + 170) cm = 5635 cm

Correct average = correct sum/total number of student = (5635/35) cm = 161 cm

 ∴ The correct average height is 161 cm.