Multiple choice

It takes 12 hours for a sailor to cover a distance of 75 km against the stream while it takes only 7.5 hours to cover the same distance in the direction of the stream. What is the speed of the stream?

  1. $8.125 km/h$
  2. $6.625 km/h$
  3. $6.25 km/h$
  4. $1.875 km/h$
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let boat speed = b and stream speed = s. Upstream: b - s = 75/12 = 6.25 km/h. Downstream: b + s = 75/7.5 = 10 km/h. Solving these equations: 2b = 16.25, so b = 8.125 km/h. Then 2s = 3.75, giving s = 1.875 km/h. Option D is correct.

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