Multiple choice

The speed of a boat in still water is 10 m/s and the speed of the stream is 6 m/s. What is the ratio of the time taken to cover a particular stretch of distance in each direction, if the boat is moving first upstream and back downstream?

  1. 4 : 1

  2. 5 : 4

  3. 2 : 1

  4. 2 : 3

  5. 8 : 1
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A Correct answer
Explanation

Upstream speed = 10 - 6 = 4 m/s. Downstream speed = 10 + 6 = 16 m/s. Time is inversely proportional to speed. Ratio of times = 16 : 4 = 4 : 1.

AI explanation

The upstream speed equals 10 minus 6, which is 4 m/s, and the downstream speed equals 10 plus 6, which is 16 m/s. Because time equals distance divided by speed, the ratio of the time taken upstream to downstream is 1 divided by 4 to 1 divided by 16, which is the same as 16 to 4. Simplifying this ratio gives 4 to 1. The result is 4 : 1.

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