The average weight of a certain number of students in a class is 55.5 kg. If 4 students with average weight 60 kg join the class, then the average weight of all students in the class increases by 360 g. The number of students in the class, initially, is:

46

Lets assume earlier total number of student = x

Sum of weights of student = 55.5x

Now total number of student = x + 4

Total weight increased = 4 x 60

As per question

(X + 4) x (55.5 + .36) = 55.5x +240

x= 46

So, initial  total number of student were 46