Multiple choice

Speed of a boat is 8 km/hr in still water and speed of the stream is 2 km/hr. If the boat takes 8 hours to go to a place and come back, then what is the distance (in km) to the place?

  1. 24

  2. 30

  3. 45

  4. 42
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let d be the distance. Downstream speed is 8+2=10 km/hr; upstream speed is 8-2=6 km/hr. The total time is d/10 + d/6 = 8. Solving for d: (3d + 5d)/30 = 8, so 8d/30 = 8, which gives d = 30 km.

AI explanation

The downstream speed is the sum of the boat's speed and the stream's speed, which is 8 + 2 = 10 km/hr, and the upstream speed is their difference, which is 8 - 2 = 6 km/hr. Let the distance to the place be D kilometers; using the formula total time equals distance divided by speed, the equation is 8 = (D / 10) + (D / 6). Solving this equation yields 8 = (3D + 5D) / 30, which simplifies to 8 = 8D / 30, so the distance is 30 km.

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