Multiple choice

A boat goes downstream and covers the distance between two ports in 4 hours, while it covers the same distance upstream in 5 hours. If the speed of the stream is 2 km/hr, find the speed of boat in still water.

  1. 16 km/hr

  2. 18 km/hr

  3. 20 km/hr

  4. 15 km/hr
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B Correct answer
Explanation

Let v be boat speed and s=2 be stream speed. (v+2)*4 = (v-2)*5. 4v + 8 = 5v - 10. v = 18 km/hr.

AI explanation

Let the speed of the boat in still water be x km/hr. Since the distance covered downstream and upstream is the same, we equate the distances using the formula distance equals speed multiplied by time. This gives us 4(x + 2) = 5(x - 2). Expanding both sides yields 4x + 8 = 5x - 10, which simplifies to x = 18. The speed of the boat in still water is 18 km/hr.

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