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    Question

    Train B can cross a ‘d’ meter long platform in 16 seconds. The speed of train B is 40% less than the speed of train A. Train A can cross a pole in 8 seconds. The ratio between the length of train A and B is 10:9 respectively. Both of the trains cross each other in 9.5 seconds. What is the value of ‘d’?

    A 140 Correct Answer Incorrect Answer
    B 120 Correct Answer Incorrect Answer
    C 210 Correct Answer Incorrect Answer
    D 160 Correct Answer Incorrect Answer
    E cannot be determined Correct Answer Incorrect Answer

    Solution

    The speed of train B is 40% less than the speed of train A.

    Let’s assume the speed of train A is 10y.

    speed of train B = 10y of (100-40)%

    = 10y of 60%

    = 6y

    The ratio between the length of train A and B is 10:9 respectively.

    Let’s assume the length of train A and B is 10z and 9z respectively.

    Train B can cross a ‘d’ meter long platform in 16 seconds.

    (9z+d)/16 = 6y

    9z+d = 96y    Eq.(i)

    Train A can cross a pole in 8 seconds.

    10z/8 = 10y

    z = 8y     Eq.(ii)

    Both of the trains cross each other in 9.5 seconds.

    (10z+9z)/9.5 = 10y+6y

    19z/9.5 = 16y

    2z = 16y

    z = 8y    Eq.(iii)

    Here Eq.(ii) and Eq.(iii) are the same. In Eq.(i) and Eq.(ii) two and three variables are available. So we cannot determine the value of any of the variables from the given information.

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