The average weight of a class of 15 boys and 10 girls is 38.4 kg. If the average weight of the boys is 40 kg, then what is the average weight of the girls?

Given that, number of boys (n₁) = 15
Numbers of girls (n₂)= 10
Average weight of boys and girls = 38.4 kg
Average of boys = 40 kg
Let average of girls be a₂
By formula, average = (na₁ + n₂ a₂) / (n₁ + n₂)
⇒ 38.4 = (15(40) + 10 x a₂)/(15 + 10)
⇒ 38.4 x 25 = 600+ 10a₂
⇒ a₂= (960 - 600)/10 = 360/10 = 36 kg