Multiple choice

A man can row the boat at $5$ km/hr in still water. If the velocity of the current is $1$ km/hr and it takes him $1$ hour to row to a place and come back, how far is the place ?

  1. $2.5$ km
  2. $3$ km
  3. $2.4$ km
  4. $3.6$ km
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Let distance be d. Downstream speed = 5+1 = 6 km/hr. Upstream speed = 5-1 = 4 km/hr. Total time = d/6 + d/4 = 1 => (2d+3d)/12 = 1 => 5d = 12 => d = 2.4 km.

AI explanation

The downstream speed is the sum of the speeds, giving 5 + 1 = 6 km/hr, and the upstream speed is the difference, giving 5 - 1 = 4 km/hr. Let the distance be d kilometers; the total time of 1 hour equals the downstream time plus the upstream time, giving d/6 + d/4 = 1. Solving this equation by finding a common denominator gives 2d + 3d = 12, so 5d = 12 and d = 2.4 km.

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