Multiple choice

A sailor travels in a boat 8 km downstream in 40 minutes and returns back to the same point in 1 hour. What is the speed of the boat in still water?

  1. 6 kmph

  2. 12 kmph

  3. 9 kmph

  4. 10 kmph
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D Correct answer
Explanation

Downstream speed = 8 km / (40/60 hr) = 12 km/hr. Upstream speed = 8 km / 1 hr = 8 km/hr. Still water speed = (12+8)/2 = 10 km/hr.

AI explanation

Using the speed formula, the downstream speed is 8 km divided by 40 minutes, which converts to 8 km divided by (2/3) hours, yielding 12 kmph. The upstream speed is 8 km divided by 1 hour, which equals 8 kmph. The speed of the boat in still water is the average of the downstream and upstream speeds, calculated as 12 plus 8, divided by 2. This gives 20 divided by 2, equaling 10 kmph. The result is 10 kmph.

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