A runs 12/3 times as fast as B. If A gives B a start of 80 m, how far must the winning post be so that A and B might reach it at the same time?

Answer: Option A

Ratio of speeds of A and B $$=\frac{5}{3}:1=5:3$$
Thus, in race of 5m, A gains 2m over B
2m are gained by A in a race of 5m
80m will be gained by A in a race of
$$\left(\frac{5}{2}\times 80\right)\text{m}=200\text{ m}$$
∴ Winning post is 200 m away from the starting point