Question

The average marks of 65 students in a class was calculated as 150. It was later realised that the marks of one of the student was calculated as 142, whereas his actual marks were 152. What is the actual average marks of the group of 65 students? (rounded off to two digits after decimal)

• A. 151.25
• B. 150.15
• C. 151.10
• D. 150.19
• E. None of the above

Answer 1

The correct option is B 150.15

Here, value of new quantity added - value of removed quantity = $\pm$ N.x
$\Rightarrow$ 152 - 142 $\pm$ N.x
$\Rightarrow$ 10 = 65.x
$\Rightarrow$ $x=\frac{10}{65}$
So, actual average = 150 + $\frac{10}{65}$
= 150 + 0.15
= 150.15