The average weight of 35 students in a class is 40 kgs. Five of the students of this class whose average weight is 42 kgs left the class. Find the average weight of the remaining 30 students.

Correct option is A

Given:
The average weight of 35 students in a class= 40kgs
Average weight of 5 students who left =42 kgs
Formula Used:
Average weight = (Total Weight )/(Number of students)
Solution:
Total weight of 35 students =35 ×40 =1400kgs
Total weight of 5 students who left = 5 × 42 = 210 kgs
Total weight of remaining students = 1400 -210 = 1190kgs
Average weight of remaining students = $$\frac{1190}{30} = 39 \frac23$$​ kgs
Alternate method:
Extra weight above average
(42-40) ×5 = 10 kgs
New average = 40 - $$\frac {10}{30}$$​ = 40 - $$\frac 13$$​ = 39$$\frac 23$$​ kgs