Multiple choice

A boat travels 28 km upstream in 7 hours and 22.5 km downstream in 4 hours 30 minutes. Then, the speed of the boat in still water and the speed of the current, respectively is

  1. 4.5 km/h and 0.5 km/h

  2. 6.5 km/h and 0.6 km/h

  3. 5.5 km/h and 5 km/h

  4. 9 km/h and 0.9 km/h

  5. None of these
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A Correct answer
Explanation

Upstream speed = 28/7 = 4 km/h. Downstream speed = 22.5 / 4.5 = 5 km/h. Boat speed = (5+4)/2 = 4.5 km/h. Current speed = (5-4)/2 = 0.5 km/h.

AI explanation

Calculate the upstream speed as 28 km divided by 7 hours, which equals 4 km/h. Calculate the downstream speed as 22.5 km divided by 4.5 hours, which equals 5 km/h. Using the boat and stream formulas, the speed of the boat in still water is (5 + 4) / 2, which equals 4.5 km/h, and the speed of the current is (5 - 4) / 2, which equals 0.5 km/h. These values match the required speeds.

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