Multiple choice

A yacht takes half time to cover a certain distance downstream than upstream. What is the ratio between speed of yacht in still water and speed of stream?

  1. 2 : 1

  2. 3 : 1

  3. 4 : 1

  4. 4 : 3
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let distance be D, speed of yacht be u, and speed of stream be v. Downstream time = D/(u+v), upstream time = D/(u-v). Given D/(u+v) = 0.5 * D/(u-v), so 2(u-v) = u+v, which simplifies to u = 3v. The ratio u:v is 3:1.

AI explanation

Let the speed of the yacht in still water be u and the speed of the stream be v. Since downstream speed is u plus v and upstream speed is u minus v, taking half the time downstream means the downstream speed is double the upstream speed. Therefore, u plus v equals 2 times (u minus v), which simplifies to u plus v equals 2u minus 2v, making u equal to 3v. The ratio of the speed of the yacht to the speed of the stream is therefore 3 : 1.

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