The average weight of a class is 45kg. If 4 new students of average 40kg joined then the average decreased by 1kg. Find the original strength of the class.

let number of students = x

Total weight = 45 × x

4 new students added

then,no. of students = x + 4

4 students average = 40

Total weight of 4 students = 40 × 4 = 160 kg

After 4 persons joined New average decreased by 1 kg

$44=\frac{45x+160}{x+4}$

44(x+4) = 45x + 160

44x + 176 = 45x + 160

x = 16

original strength = 16