question_answer

The ratio of the number of boys and girls in a college is 7: 8. If the percentage increase in the number of boys and girls be 20% and 10% respectively, what will be the new ratio?

A) 8 : 9

B) 17: 18

C) 21: 22

D) Cannot be determined

Correct Answer: C

Solution :

Originally, let the number of boys and girls in the college be 7x and 8x, respectively. Their increased number is (120% of 7x) and (110% of 8x).

i.e.        \[\left( \frac{120}{100}\times 7x \right)\] and \[\left( \frac{110}{100}\times 8x \right)\]

i.e.        \[\frac{42x}{5}\] and \[\frac{44x}{5}\]

Required ratio \[=\,\,\frac{42x}{5}:\frac{44x}{5}=21:22\]