Multiple choice

Arun went boating in a river. Speed of Arun in still water is 7 km/hr and the river is running at a rate of 4 km/hr. The total time taken by him to go to a certain place and come back is 28 hours. What is the total distance travelled by him?

  1. 127 km

  2. 66 km

  3. 132 km

  4. 124 km

  5. 150 km
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Downstream speed = 7 + 4 = 11 km/hr. Upstream speed = 7 - 4 = 3 km/hr. Let distance be D. Total time = D/11 + D/3 = 28. (3D + 11D) / 33 = 28. 14D / 33 = 28. D = 66. Total distance (round trip) = 66 * 2 = 132 km.

AI explanation

Using the boat and stream formula, the downstream speed is 7 + 4 = 11 km/hr and the upstream speed is 7 - 4 = 3 km/hr. Let the one-way distance be x, so the total time equation is x/11 + x/3 = 28 hours. Solving this gives (3x + 11x)/33 = 28, which simplifies to 14x/33 = 28 and x = 66 km. The total distance for the round trip is 2x, which is 132 km.

Keep practicing — related questions