A person travels a certain distance at 3 km/h and reaches 15 min late

A person travels a certain distance at 3 km/h and reaches 15 min late. If he travels at 4 km/h, he reaches 15 min earlier. The distance he has to travel is

  1. 4.5 km
  2. 6 km
  3. 7.2 km
  4. 12 km

Answer

Let the time taken to travel at speeds 3 km/h and 4 km/h be t1and t2 respectively.

So, t1 - t2 = 15 - (-15) = 30 minutes = 0.5 h

Now, let the distance travelled be = x km

So, (x / 3) - (x / 4) = 0.5 

⇨ x = 6 km

The correct option is B.