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    Question

    The time taken by train B to cross a platform of 120

    metres is 3 sec less than the time taken by train A to cross the same platform. The sum of length of train A and B is 600 metres. The ratio of speeds of trains A and B is 3:2 respectively. Find the speed of train B.
    A 25 m/s Correct Answer Incorrect Answer
    B 45 m/s Correct Answer Incorrect Answer
    C 36 m/s Correct Answer Incorrect Answer
    D Can't be determined Correct Answer Incorrect Answer
    E None of these Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the length of train A = LA  and length of train B = LB  respectively, Speed of train A = 3x, Speed of train B = 2x.

    From the problem:

    Substitute LB = 600 − LA into the equation and simplify: 2LA − 3LB − 120 = 18x,

    Solve to get LA = 18x/5 + 384. Use this relation to calculate 'x' or LA with additional constraints or assumptions about 'x' is not mention  Hence, it Can't be determined

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