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    Question

    Two runners M and N run in opposite directions on a

    circular track of 1500 metres. M runs at 30 m/s and N at 45 m/s. After how many seconds will they both be at the starting position together?
    A 120 secs Correct Answer Incorrect Answer
    B 100 secs Correct Answer Incorrect Answer
    C 255 secs Correct Answer Incorrect Answer
    D 133 secs Correct Answer Incorrect Answer

    Solution

    ATQ,

    Time taken by M to finish one round = (1500 / 30) = 50 seconds

    Time taken by N to finish one round = (1500 / 45) = 33.33 seconds (100/3)

    The time taken to meet at the starting point = LCM of (50, 100/3)

    Convert both to fractions: 50 = 150/3

    LCM of (150/3, 100/3) = 300/3 = 100 seconds

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