Question

The speed of motorboat in still water is 34 km/hr. It takes 6 hours to go 120 km upstream. Find the time taken by the motorboat to return the same distance.

A 4.8 hours Correct Answer Incorrect Answer
B 2.5 hours Correct Answer Incorrect Answer
C 3.2 hours Correct Answer Incorrect Answer
D 5 hours Correct Answer Incorrect Answer

Solution

Let the speed of stream = x km/hr The speed of the motorboat in upstream = (34 – x) km/hr Distance = speed × time => 120 = (34 – x) × 6 => x = 14 km/hr While returning the motorboat will go in downstream, The speed of the motorboat in downstream = (34 + 14) = 48 km/hr The required time taken = 120/48 = 2.5 hours

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