Question

In a class there are 90 students and their average marks in the annual examination is 50. If the average marks of passed students is 70 and average marks of failed students is 40, then find out the number of the students failed in the examination

Answer 1

The number of the students failed in the examination is 60.

Explanation

Suppose, the number of the students failed in the examination is  $x$

As there are total 90 students in the class, so the number of the students passed in the examination will be:  $(90-x)$

Average marks of all 90 students is 50. So, the total marks of 90 students $=(90*50)=4500$

Given that, the average marks of passed students is 70 and average marks of failed students is 40. So, the equation will be.........

$70(90-x)+40x=4500\\ \\ 6300-70x+40x=4500\\ \\ -30x=4500-6300=-1800\\ \\ x=\frac{-1800}{-30}=60$

So, the number of the students failed in the examination is 60.