Question
Ram makes four trips of equal distances. His speed on
first trip was 120 km/hr and in each subsequent trip his speed was half of the previous trip. What is the average speed of Ram in these four trips?Solution
Let us assume the distance on the first trip is d The total distance = 4d The speed on first trip = 120 km/h The speed on second trip = 60 km/h The speed on the third trip = 30 km/h The speed on the fourth trip = 15 km/h The total time is taken by Ram in the whole trip = [(d/120) + (d/60) + (d/30) + (d/15) + (15d/120)] = (d/8) The average speed = (4d/d)/(d/8) = 32 km/hr
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