Question

A boy can swim a certain distance downstream in 3 hours and return in 8 hours. If the rate of stream is 5 kmph then what is the speed of boy in still water?

A 11 kmph Correct Answer Incorrect Answer
B 10 kmph Correct Answer Incorrect Answer
C 17 kmph Correct Answer Incorrect Answer
D 19 kmph Correct Answer Incorrect Answer

Solution

Let the speed of the boy in still water be x kmph. Then, (x + 5) × 3 = (x – 5) × 8 => 3x + 15 = 8x - 40 => 5x = 55  => x = 11 kmph

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