Question

In a school 1/5th of girls and 1/4th of the boys are under 12 years of age. If the total strength of the school is 1000 and number of girls is 2/5th of the total, what is the strength of the school, who are 12 years or more of age?

Answer 1

Answer:

Since out of total strength 1000, 2/5 are girls, therefore

$no \: of \: girls \: = \frac{2}{5} \times 1000 = 400 \\ so \\ \: no \: of \: boys \: = 1000 - 400 = 600 \\ since \: \frac{1}{5} \: of \: girls \: and \: \frac{1}{4} \: of \: the \\ \: boys \: are \: under \: 12 \: years \: of \: age \\ therefore \: total \: strength \: under \\ \: 12 \: years \: of \: age \: \\ = \frac{1}{5} \times 400 + \frac{1}{4} \times 600 \\ = 80 + 150 \\ = 230$