Question

A man rows a certain distance downstream in 5 hours and back to the same point in 8 hours. If the speed of the stream is 4.5 km/hr then what is the speed of the man in still water?

A 15.5 km/hr Correct Answer Incorrect Answer
B 1 km/hr Correct Answer Incorrect Answer
C 19.5 km/hr Correct Answer Incorrect Answer
D 14.5 km/hr Correct Answer Incorrect Answer
E None of these Correct Answer Incorrect Answer

Solution

Let the speed of the man in still water be x km/hr. Downstream speed = (x+ 4.5) km/hr. Upstream speed = (x- 4.5) km/hr. (x+ 4.5) × 5 = (x- 4.5) × 8 5 x + 22.5 = 8 x - 36 3 x = 58.5 ∴ x = 19.5 km/hr.

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