Multiple choice

A race-boat covers a distance of 60 km downstream in one and a half hour. It covers this distance up stream in 2 hours. The speed of the race-boat in still water is 35 km/hr, Find the speed of the stream.

  1. 5 km/hr

  2. 5 m/s

  3. 0.5 Km/s

  4. 6 Km/m
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A Correct answer
Explanation

Downstream speed = 60 / 1.5 = 40 km/hr. Upstream speed = 60 / 2 = 30 km/hr. Let boat speed be B and stream speed be S. B + S = 40, B - S = 30. 2S = 10, S = 5 km/hr.

AI explanation

The downstream speed of the race-boat is the total distance divided by the time, so 60 km divided by 1.5 hours equals 40 km/hr. The upstream speed is 60 km divided by 2 hours, which equals 30 km/hr. Using the formula for the speed of a stream, which is half the difference of the downstream and upstream speeds, we calculate (40 minus 30) divided by 2, which equals 5 km/hr.

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