Multiple choice

A boat will take how much time to cross the river against the stream of the river? A. In still water the speed of the boat is 15 km/hr. B. The width of the river is 8 km. C. The speed of the stream is 2 km/hr.

  1. Only A

  2. Only B

  3. Only C

  4. All A, B and C are required to answer the question.

  5. A, B and C are not sufficient to answer the question.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Time = distance / speed. Against stream: effective speed = boat speed - stream speed. Statement A gives boat speed (15 km/hr). Statement C gives stream speed (2 km/hr). So effective speed = 15 - 2 = 13 km/hr. Statement B gives distance (8 km). Time = 8/13 hours. All three statements are required; none alone gives the time.

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