Multiple choice

The speed of a boat in still water is 4 km/hr and the speed of current is 2 km/hr. If the time taken to reach a certain distance upstream is 9 hours, the time it will take to go to the same distance downstream is

  1. 3.5 hours

  2. 2.5 hours

  3. 2 hours

  4. 3 hours

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

Boat speed = 4, current = 2. Upstream speed = 4-2 = 2 km/hr. Distance = 2 * 9 = 18 km. Downstream speed = 4+2 = 6 km/hr. Time = 18 / 6 = 3 hours.

AI explanation

The upstream speed is the difference between the boat's speed and the current's speed, which is 4 km/hr minus 2 km/hr, equaling 2 km/hr. The downstream speed is the sum of the boat's speed and the current's speed, which is 4 km/hr plus 2 km/hr, equaling 6 km/hr. The distance traveled upstream is 2 km/hr multiplied by 9 hours, giving 18 km. The time taken to travel the same 18 km downstream is 18 km divided by 6 km/hr, which equals 3 hours. The result is 3 hr.

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