Two man start together to walk a certain distance, one at 4 km/hr and another at 3 km/hr. The former arrives half an hour before the latter. Find the distance.

Two man start together to walk a certain distance, one at 4 km/hr and another at 3 km/hr. The former arrives half an hour before the latter. Find the distance.
[A]6 km
[B]7 km
[C]8 km
[D]9 km

6 km
If the required distance be x km, then
\frac{x}{3} - \frac{x}{4} = \frac{1}{2}
=> \frac{4x-3x}{12} = \frac{1}{2}
=> \frac{x}{12} = \frac{1}{2}
=> x = 6 km
Hence option [A] is correct answer.

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