Multiple choice

In each of the following questions, a question is followed by three statements numbered I, II and III. Read all the statements and answer accordingly. What is the speed of the train? Statement I: The train crosses 300 metres long platform in 45 seconds. Statement II: The train crosses another stationary train of same length in 60 seconds. Statement III: The train crosses a signal pole in 30 seconds.

  1. Only III and I or II

  2. Any two of the three

  3. Only II and I or III

  4. Only I and II

  5. Only I and II or III
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

Let L be train length, S be speed. From I: L+300 = 45S. From II: 2L = 60S, so L = 30S. From III: L = 30S. Substituting L=30S in I: 30S + 300 = 45S, so 15S = 300, S = 20 m/s. We need two statements: either I and II (gives L and S), or I and III (same as II), or II and III (both give L=30S, need one more). So 'Only I and II or III' means we need statement I plus either II or III.

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