If A runs 3 times as fast as B and A gives B a start of 60 m, then how far must be winning post on tracks so that A and B reach at same time?
Answer & explanation
Correct answer: option 2
$\text{Let speed of B}=v.$
$\text{Speed of A}=3v.$
$\text{Let distance of race}=D.$
$\text{B runs }D-60\text{ metres, A runs }D\text{ metres}.$
$\text{Equal time condition:}$
$\frac{D}{3v}=\frac{D-60}{v}.$
$D=3(D-60).$
$D=3D-180.$
$2D=180.$
$D=90.$
$\text{Winning post must be }90\text{ m away.}$