A runs 5 times faster than B. If A gives B a start of 100m, how far must the goal be so that A and B reach there at the same time.
Answer & explanation
Correct answer: option 3
$\text{Speed ratio }A:B=5:1.$
$\text{Let total distance}=D.$
$\text{B gets a start of }100\text{ m, so B runs }(D-100).$
$\text{Equal time condition:}$
$\frac{D}{5}=\frac{D-100}{1}.$
$D=5(D-100).$
$D=5D-500.$
$4D=500.$
$D=125.$
$\text{Distance of goal from A}=125\text{ m}.$