Multiple choice

Sameer can row certain distance downstream in 24 h and can come back covering the same distance in 36 h. If the stream flows at the rate of 12 km/h. find the speed of Sameer in still water.

  1. 30 km/h

  2. 15 km/h

  3. 40 km/h

  4. 60 km/h
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let v be speed in still water and c = 12. Downstream speed = v+12, upstream = v-12. Distance D = (v+12)*24 = (v-12)*36. 24v + 288 = 36v - 432. 12v = 720, so v = 60 km/h.

AI explanation

Let the total distance be X kilometers; the downstream speed is X divided by 24 and the upstream speed is X divided by 36. The speed of the boat in still water is half the sum of these speeds, so the calculation is 0.5 multiplied by (X divided by 24 plus X divided by 36), which simplifies to 5X divided by 144. The given stream speed is 12 kmph, which is half the difference of the downstream and upstream speeds, so 0.5 multiplied by (X divided by 24 minus X divided by 36) equals 12, and solving this yields X equal to 864. Substituting X back into the boat speed formula gives 5 multiplied by 864 divided by 144, resulting in a still water speed of 60 km/h.

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