Question

Choose the correct answer from the alternatives given.
Two men start together to walk a certain distance, one at 4 km/h and another at 3 km/h. The former arrives half an hour before the latter. Find the distance(in km).

Answer 1

Let the time taken by the man travelling at 4 km/h be t hours, then the time taken by the man travelling at 3 km/h will be $(t+\frac{1}{2})$ hours
As the distance travelled by them is same then the speed will be inversely proportional to the time taken.
$\frac{4}{3}=\frac{t+\frac{1}{2}}{t}$

$4t=3t+\frac{3}{2}$

$t=\frac{3}{2}$ hours
The man travelling at 4 km\h travels for $\frac{3}{2}$ hours hence the distance will be $4\times \frac{3}{2}=6km$