The average weight of a class of 15 boys and 10 girls is

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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 ?

1. 36.5 kg
2. 35 kg
3. 36 kg
4. 35.6 kg

Correct Option: C

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