The correct answer is (C):
Let the distance from his home to his hostel be x miles.
Time taken on his onward journey = x/60 hours
Time taken on his return journey = (x/2)/25 + (x/2 + 5)/50
Given, his return journey took 0.5 hours more than his onward journey
⇒ x/60 + 0.5 = x/50 + (x/2 + 5)/50
Upon solving, x = 30
Therefore, total distance travelled = 30 + 15 + 20
= 65 miles.