Multiple choice

Passage

Directions : The following question consists of statements A, B and C. You have to determine the statement(s) which is/are necessary to answer the question.

A man can row a distance of x km upstream in 3.5 hours. Find his speed in still water. A. He covers a distance of 84 km downstream in 6 hours. B. He covers the distance of x km downstream in 2.5 hours. C. The speed of the current is 2 kmph.

  1. Any two of them

  2. Either B or C only

  3. Any of them

  4. All statements are required

  5. None of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Let u be speed in still water and v be speed of current. Upstream speed is u - v = x / 3.5. Downstream speed is u + v = x / 2.5 (using statement B). With statement C, v = 2. We have two equations with two variables (u and v) if we use any two of the three statements. For example, using A and B allows finding x, and then using C or the relationship between upstream/downstream speeds allows finding u.

AI explanation

The man's upstream speed is x divided by 3.5 km/hr. Using the formula where the speed in still water is half the sum of the upstream and downstream speeds, we need the downstream speed. Statements A and B together give the downstream speed in different scenarios or a specific distance, while statements B and C directly give the downstream time for distance x and the current speed to find the still water speed. Statements A and C can also be used to set up equations relating the unknown distance x and the upstream and downstream speeds. Therefore, any two of the three statements are sufficient to find his speed in still water.

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