Multiple choice

The time taken by a boat going a certain distance upstream is 4 times the time taken by it covering the same distance downstream. What is the ratio of speed of the boat in still water to that of current?

  1. 4 : 3

  2. 5 : 3

  3. 5 : 4

  4. 6 : 3

  5. 6 : 4
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let boat speed be B and current be C. Upstream time = D/(B-C), Downstream time = D/(B+C). D/(B-C) = 4 * D/(B+C) => B+C = 4B - 4C => 3B = 5C => B/C = 5/3.

AI explanation

Let the speed of the boat in still water be B and the speed of the stream be S. We are given that the upstream time is 4 times the downstream time for the same distance, meaning the downstream speed is 4 times the upstream speed. The upstream speed is B minus S and the downstream speed is B plus S, so B plus S equals 4 times B minus S, which simplifies to 5S equals 3B. Solving this ratio gives the ratio of the speed of the boat in still water to the speed of the current as 5 to 3.

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