Multiple choice

Directions: The following questions are accompanied by three statements A, B and C. You have to determine which statement(s) is/are sufficient necessary to answer the questions and mark your answer accordingly. What is the speed of train P? (A) If train P and train Q move towards each other, they can cross each other in 4.5 sec. and if these trains move on parallel lines on same direction, then train P overtake train Q in 31.5 sec. (B) Train Q can cross a man running in opposite direction at 10 m/sec on 5 sec and also train Q can cross a man running in same direction at 10 m/sec in 7 sec. (C) Train P can cross a platform of double its length in 10.5 sec and can cross a pole in 3.5 sec.

  1. Any two of them

  2. A and B together only

  3. Either A and B or B and C

  4. Any one of them

  5. Either A or B and C together
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Statement A provides relative speeds. Statement B provides the speed of train Q. Statement C provides the length of train P. To find the speed of train P, we need its length and relative speed information. A and B together allow us to find the speed of both trains.

AI explanation

Statement B alone allows you to find the length and speed of train Q by using the relative speed formula. If L is the length of Q, then L = (s + 10) * 5 and L = (s - 10) * 7, meaning s = 60 m/sec and L = 350 m. Statement A provides the relative crossing times for P and Q, giving two equations: 350 + length of P = 4.5 * (speed of P + 60) and 350 + length of P = 31.5 * (speed of P - 60). Solving this system yields the speed of train P. Therefore, A and B together only are sufficient.

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