Question

    A can finish a job in 20 days while B can finish same

    job in 30 days. A and B both worked for 5 days and C joins them. In next 3.5 days, all three have managed to complete the job. Find in how many days C alone can finish the job.
    A 9 days Correct Answer Incorrect Answer
    B 3 days Correct Answer Incorrect Answer
    C 12 days Correct Answer Incorrect Answer
    D 24 days Correct Answer Incorrect Answer

    Solution

    A's 1 day's work = 1/20 B's 1 day's work = 1/30 (A + B)’s 1 day's work = 1/20 + 1/30 = 1/12 (A + B)’s 5 day's work = 5/12 Remaining fraction of work after 5 days = 1 – 5/12 = 7/12 Let C's 1 day's work be 1/M. Then, ⇒  (1/12 + 1/M) = 7/12 × 1/3.5 ⇒  (1/12 + 1/M) = 1/6 ⇒  1/M = 1/12 C alone can complete the work in 12 days.

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