There are some children in a camp and their average weight is 40 kg. If 5 children with average weight 36 kg join the camp or if 5 children with average weight 43.2 kg leave the camp, the average weight of children in both cases is equal. How many children are there in the camp, initially?

45

let No. of children in a camp = x

Sum of weights of children = 40x

Sum of weights of children when 5 more joins = 36 x 5 + 40x = 180 + 40x

Sum of weights of children when 5 leaves the camp = 40x - 43.2 x 5 = 40x - 216

Given, \(\frac{180 + 40x}{x + 5}\) = \(\frac{40x - 216}{x - 5}\)

        ⇒ 20x + 900 = 16x + 1080

            x = 45