UPSC 2015 CDS I Math Paper

Let the speed of B be x m/s
Therefore, speed of A=

5

3

xm/s
Suppose A reaches the winning post after t seconds.
Distance covered by A in t seconds = 80 m + Distance covered by B in t seconds
∴

5

3

x×t=80+x×t
⇒

5

3

xt−xt=80
⇒

2

3

xt=80
⇒xt=120m
Therefore, distance of the winning post from the starting point