Multiple choice

Raj can row a certain distance downstream in 12 hours and can return the same distance in 18 hours. If the stream flows at the rate of 6 km/hr, find the speed of Raj in still water.

  1. 15 km/hr

  2. 20 km/hr

  3. 25 km/hr

  4. 30 km/hr
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let downstream speed = (d+6) km/hr and upstream speed = (d-6) km/hr where d is speed in still water. Distance is same: 12(d+6) = 18(d-6). Solving: 12d+72 = 18d-108, so 6d = 180 and d = 30 km/hr. The distance cancels out when equating both expressions.

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