Multiple choice

A boat moving upstream covers a distance of 40 km in 10 hours. When moving downstream, it covers a distance of 72 km in 9 hours. Find the time taken by the boat to cover a distance of 48 km in still water.

  1. 6 hours

  2. 7 hours

  3. 7.5 hours

  4. 8 hours

  5. 9.5 hours
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Upstream speed = 40/10 = 4 km/h. Downstream speed = 72/9 = 8 km/h. Still water speed = (8 + 4) / 2 = 6 km/h. Time to cover 48 km = 48 / 6 = 8 hours.

AI explanation

The upstream speed is 40 km in 10 hours, which equals 4 km/hr, and the downstream speed is 72 km in 9 hours, which equals 8 km/hr. The speed of the boat in still water is the average of these two speeds, yielding (4 + 8) / 2 = 6 km/hr. To cover 48 km in still water at 6 km/hr, the boat takes 48 / 6 = 8 hours. The result is 8 hours.

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