A man walks to a viewpoint and returns to the starting point by his car maintaining a constant speed and thus, takes a total time of 4 hours 45 minutes. He would have gained 2 hours by driving both ways. How long would it have taken for him to walk both ways with the same walking speed?

Correct option is D

Given:

A man walks to a viewpoint and returns by car.

Total time for this trip = 4 hours 45 minutes = 4.75 hours.

If he had driven both ways he would have saved 2 hours.

Find time to walk both ways (same walking speed).

Formula Used:

time = distance / speed

​Solution:​

Let one-way distance = D, walking speed = w, driving speed = v

Now, 

D/w + D/v = 4.75 ..............(1)

2D/v = (D/w + D/v) − 2 ...................(2)

From second equation:

2D/v = 4.75 − 2 = 2.75 => D/v = 1.375 hours.

Substitute into first:

D/w + 1.375 = 4.75 => D/w = 4.75 − 1.375 = 3.375 hours.

Walking both ways time = 2 × (D/w) = 2 × 3.375 = 6.75 hours = 6 hours 45 minutes

Alternate Solution (short trick):