Sohan makes four trips of equal distances. His speed on the first trip was 240 km/hr and in each subsequent trip, his speed was half of the previous trip. What is the average speed of Sohan in these four trips?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 64 km/hr.
Let the Distance traveled be D.
Speed for trip 1 = 240 km/h
Speed for trip 2 = 120 km/h
Speed for trip 3 = 60 km/h
Speed for trip 4 = 30 km/h
Time taken for trip 1 = D/240
Time taken for trip 2 = D/120
Time taken for trip 3 = D/60
Time taken for trip 4 = D/30
Total time = D/240 + D/120 + D/60 + D/30 = D/16
Total distance = 4D
Average speed = 4D/(D/16) = 64 km/h