Answer: 1/2
Explanation: Mr.Wagles at first falls asleep when the bus still has twice as far to go as it has already gone. So he starts sleeping at 1/3 of the total distance.
Next: Halfway through the trip he wakes up as the bus bounces over some bad potholes. So he wakes up 1/2 of the total distance.
So he had slept 1/2-1/3=1/6 (First part)
Then, When he finally falls asleep again, the bus still has half the distance to go that it has already travelled. Fortunately, Mr. Wagle wakes up at the end of his trip. So he again starts sleeping at 2/3 till end.
So he had slept 1-2/3=1/3(Second part)
Finally, 1/6+1/3=1/2.
Idhudhanga.