Question 293812
let the number of students be x. The sum of all their ages = 40x

120 joined 

total is x+120

The sum of all their ages = 40x+ 120*32

=40x + 3840

average age now is 36

40x+3840  / x+120 =36

40x+3820 = 36(x+120)

40x+3840 =36x + 4320

40x-36x= 4320-3840

4x= 480

x= 120

initially there were 120. 120 joined. so total isd 240 students