Question

    'P' and 'Q' can finish a piece of

    work in 45 days and 90 days, respectively. 'P' starts working alone, and 'Q' joins after 'r' days, ensuring that the entire work is completed in '2r' days. Find the value of 'r'.
    A 22 Correct Answer Incorrect Answer
    B 18 Correct Answer Incorrect Answer
    C 10 Correct Answer Incorrect Answer
    D 12 Correct Answer Incorrect Answer

    Solution

    ATQ,

    Let the total work be 90 units. {LCM of 45 and 90} Efficiency of 'E' = 90 ÷ 45 = 2 units/day Efficiency of 'F' = 90÷ 90 = 1 units/day So, 2r + 2r + 1r = 90 Or, 5r = 90 Therefore, r = 18

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