Multiple choice

Directions: In this question, you have to find out which of the following statements is/are sufficient for determining the answer of the given question. What is the speed of the stream? I. The boat covers 48 km in 12 hours moving upstream. II. The boat covers 48 km in 6 hours moving downstream. III. The ratio between the speeds of the boat and the stream is 6 : 2, respectively.

  1. Only I and II

  2. Any two of the statements

  3. Only II and either I or III

  4. Either II or III

  5. All I, II and III
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Upstream speed = 48/12 = 4 km/h. Downstream speed = 48/6 = 8 km/h. Speed of stream = (Downstream - Upstream) / 2 = (8-4)/2 = 2 km/h. We only need two of the three statements to solve this.

AI explanation

Using the relative speed formula, statement I provides the upstream speed as 48 divided by 12, which equals 4 km/h. Statement II provides the downstream speed as 48 divided by 6, which equals 8 km/h, and taking these two together yields the stream speed of (8 - 4) / 2, equaling 2 km/h. Statement III provides the ratio of boat to stream speeds, allowing you to form a solvable system of equations with either the upstream or downstream speed. Since any combination of two statements provides enough variables to solve for the stream speed, any two of the statements are sufficient.

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