Multiple choice

Directions: Each of the following questions consists of a question followed by three statements I, II and Ill. You have to study the question and the statements and decide which of the statement(s) is/are necessary to answer the question. What is the speed of a boat in still water? I. The boat covers 12 km in 2 hours downstream. II. The boat covers the same distance in 4 hours upstream. III. The speed of the stream is one-third that of the boat in still water.

  1. Both I and II

  2. I and either II or III

  3. All I, II and III

  4. Data insufficient

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

Statement I gives the downstream speed as 6 km/h. With statement II, the upstream speed is 3 km/h, so the still-water speed is 4.5 km/h. With statement III, the stream speed is one-third of the boat speed, which also determines the still-water speed from statement I, so I and either II or III are sufficient.

AI explanation

To find the speed of the boat in still water, we need both the downstream speed and the upstream speed, or one of these speeds alongside the stream speed. Statement I provides the downstream speed as 12 divided by 2, which is 6 km/hr. Statement II provides the upstream speed as 12 divided by 4, which is 3 km/hr; therefore, I and II together are sufficient. Additionally, if we use statement I and statement III, we can set up the equation 6 = speed of boat + one-third of the boat speed, which yields the boat speed; thus, I and either II or III are necessary.

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