Multiple choice

A boat can cover certain distance in downstream in 1 hr. and it takes 1½ hr. to cover same distance in upstream. If speed of the stream is 3 kmph, then what will be time taken by the boat to travel a distance of 75 km in still water?

  1. 5.5 hours

  2. 4 hours

  3. 3 hours

  4. 5 hours
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Let boat speed in still water = b km/hr. Downstream speed = b + 3, upstream speed = b - 3. Since distance is same: (b+3) × 1 = (b-3) × 1.5. Solving: b + 3 = 1.5b - 4.5, so 7.5 = 0.5b, giving b = 15 km/hr. Time for 75 km in still water = 75/15 = 5 hours.

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