Multiple choice

It takes Rahul thrice as long to row up as to row down the river. If speed of the boat is 5.5 kmph, then find the speed of the stream.

  1. 1.25 kmph

  2. 2.75 kmph
    1. 25 kmph

  4. 3 kmph

  5. None of these
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let v be the speed of the boat and u be the speed of the stream. Upstream speed is v-u and downstream speed is v+u. Given 3(v-u) = v+u, we get 3v-3u = v+u, so 2v = 4u, or v = 2u. With v = 5.5, u = 2.75 kmph.

AI explanation

Since Rahul takes thrice as long to row upstream as downstream, his upstream speed is one-third of his downstream speed, meaning the ratio of upstream to downstream speed is 1:3. Using the stream speed formula of half the difference between downstream and upstream speeds, we get (3 units minus 1 unit) divided by 2, which equals 1 unit. Given the still water boat speed of 5.5 kmph represents the average of 1 and 3 units (which is 2 units), 1 unit equals 5.5 divided by 2, resulting in a stream speed of 2.75 kmph.

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