Multiple choice

The following questions are accompaniedly three statement I, II and III. You have to determine which statement (s) is/are necessary/sufficent to answer the question? What is the speed of the train ? (I) The train crosses a tree in 13 seconds. (II) The train crosses a platform of length 250 m. in 27 seconds. (III) The train crosses another train running in the same direction in 32 seconds.

  1. Only I and II

  2. Only II and III

  3. Only I and III

  4. All I, II and III

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

From I: train length L = 13×speed. From II: L + 250 = 27×speed. Combining: 13s + 250 = 27s, so 14s = 250, speed = 250/14 m/s. Statements I and II together are sufficient. Statement III involves another train with unknown length/speed, so it doesn't help without additional information.

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