Multiple choice

A boat covers $6$ km in an hour in still water. It takes thrice as much time in covering the same distance against the current. What is the speed of the current ?

  1. $2$ km/hr
  2. $3$ km/hr
  3. $4$ km/hr
  4. $5$ km/hr
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Speed in still water (b) = 6 km/hr. Let current speed be c. Downstream speed = 6+c, Upstream speed = 6-c. Time taken = Distance / Speed. Time against current = 6 / (6-c). Time in still water = 6 / 6 = 1. Given 6/(6-c) = 3 * 1. So 6 = 18 - 3c, 3c = 12, c = 4.

AI explanation

The speed of the boat in still water is 6 km/hr, and it takes thrice as much time to cover the distance against the current, meaning its upstream speed is one-third of the still water speed. Therefore, the upstream speed is 2 km/hr. The speed of the current is found by subtracting the upstream speed from the still water speed, which gives 6 minus 2, resulting in 4 km/hr.

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