Multiple choice

A boat takes $20$ hours to cover a certain distance upstream and come back to the starting point downstream. If the speed of the boat in still water is $8$ km/hr and speed of current is $4$km/hr. What is the distance it covers upstream ?

  1. $45$ km
  2. $60$ km
  3. $75$ km
  4. $80$ km
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let distance be D. Upstream speed = 8 - 4 = 4 km/h. Downstream speed = 8 + 4 = 12 km/h. Time = D/4 + D/12 = 20. (3D + D) / 12 = 20. 4D = 240. D = 60 km.

AI explanation

The upstream speed equals 8 minus 4, which is 4 km/hr, and the downstream speed equals 8 plus 4, which is 12 km/hr. With distance as D, the time equation is D/4 plus D/12 equals 20. Solving this gives D equals 60 km.

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