The ration of the number of boys and girls in a college is 7:8. If the percentage is increase in the number of boys and girls be 20% and 10% respectively. What will be the new ration?  Choose one.
A) 5 : 7  B) 15 : 21  C) 21 : 22  D) 13 : 17  E) 23 : 42

Rationale: let the number of boys and girls be 7 x and 8 x their increased number is 120 % of 7 x and 110 % of 8 x 7 x * 120 / 100 and 8 x * 110 / 100 42 x / 5 and 44 x / 5 required ratio = 42 x / 5 : 44 x / 5 = 21 : 22 answer is c
Answer: C