Multiple choice

A boat takes 6 hours to cover a certain distance going upstream, and 4 hours to cover the same distance going downstream. Find the ratio of the speed of the boat in still water to the speed of the stream.

  1. 2 : 3

  2. 5 : 1

  3. 5 : 2

  4. 5 : 3

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

Let boat speed be b and stream speed be s. Upstream speed (b-s) = D/6. Downstream speed (b+s) = D/4. So 6(b-s) = 4(b+s) -> 6b - 6s = 4b + 4s -> 2b = 10s -> b/s = 5/1.

AI explanation

Let the distance be D; the downstream speed is D/4 and the upstream speed is D/6, making the speed of the boat in still water equal to (D/4 + D/6) divided by 2, which simplifies to 5D/24. The speed of the stream is half the difference of the two speeds, calculated as (D/4 - D/6) divided by 2, which simplifies to D/24. The ratio of the speed of the boat in still water to the speed of the stream is therefore 5 to 1.

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