A motor boat covers a certain distance downstream in 5 hours but takes 6 hours to return upstream to the starting point. If the speed of the stream is 4 km/h, then what is the speed of the motor boat in still water?

A40 km/h

B42 km/h

C44 km/h ✓ Correct

D46 km/h

Correct answer: (C) 44 km/h

Explanation

The boat's speed in still water is 44 km/h.

Distance is equal, so (b + 4) x 5 = (b - 4) x 6.

5b + 20 = 6b - 24.

b = 44 km/h.

Downstream speed 48 and upstream 40 confirm equal distance.

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