Multiple choice

Directions: The following problem consists of a question followed by three statements (A), (B) and (C). You have to determine which statement(s) is/are sufficient/necessary to answer the question. What would be the rate of flow of river? (A) The speed of a motorboat in still water is 4 km/hr. (B) It took 80 hours in total to travel downstream and then return after covering a distance of 70 km altogether. (C) Downstream speed > Speed of the motorboat in still water

  1. Only statement A is sufficient to answer the question.

  2. Both statements A and B are required to answer the question.

  3. Only statement B is sufficient to answer the question.

  4. None of the statements is sufficient to answer the question.

  5. All three statements together are sufficient to answer the question.
Reveal answer Fill a bubble to check yourself
B Correct answer
AI explanation

Using statements A and B together, let the rate of flow of the river be r km/hr, making the downstream speed (4 + r) km/hr and the upstream speed (4 - r) km/hr. Since the total distance is 70 km altogether, the boat travels 35 km downstream and 35 km upstream. The equation is (35 / (4 + r)) + (35 / (4 - r)) = 80 hours, which can be solved to find the rate r. Statement A alone lacks total time, and statement B alone lacks the motorboat speed, so both are required to answer the question.

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