Multiple choice

A boat covers a distance of 135 km downstream in 9 hours. To cover the same distance upstream, the boat takes 6 hours longer. What is the speed of the man in still water?

  1. 12 kmph

  2. 10 kmph

  3. 14 kmph

  4. 15 kmph

  5. 18 kmph
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A Correct answer
Explanation

Downstream speed = 135 / 9 = 15 km/hr. Upstream time = 9 + 6 = 15 hours. Upstream speed = 135 / 15 = 9 km/hr. Speed of man = (15 + 9) / 2 = 12 km/hr.

AI explanation

The downstream speed is 135 km divided by 9 hours, which equals 15 kmph, and the upstream speed is 135 km divided by 15 hours (9 plus 6), which equals 9 kmph. Using the boat speed formula, the speed in still water is the average of the downstream and upstream speeds. Adding 15 and 9 gives 24, and dividing by 2 results in 12 kmph.

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