Question

A man leaves his home and walks at a speed of 12 km per hour, reaching the railway station 10 minutes after the train had departed. If instead he had walked at a speed of 15 km per hour, he would have reached the station 10 minutes before the train's departure. The distance (in km) from his home to the railway station is

• A. 26
• B. 18
• C. 16
• D. 20

Answer 1

Answer: (D)

20

Answer 2

In the second case, the speed is $\frac{5}{4}$ times the speed in the first case.
Consequently, the time would be $\frac{4}{5}$ times the time, which is equivalent to being $\frac{1}{5}$ less. This one-fifth is 20 minutes.
Therefore, the time taken in the first case is 100 minutes.
The distance $=12\times\frac{5}{3}\ km=20\ km$