Multiple choice

If A ,B and C can do a job working alone in 12, 18 an 36 days respectively. They all together work for 2 days, then B quits. How many days will A and C take to finish the rest of the amount ?

  1. 6 days

  2. 5 days

  3. 8 days

  4. 9 days
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Combined rate of A, B, C = (1/12 + 1/18 + 1/36) = (3+2+1)/36 = 6/36 = 1/6. In 2 days, they complete 2×(1/6) = 1/3 of work. Remaining work = 1 - 1/3 = 2/3. After B quits, A + C rate = (1/12 + 1/36) = (3+1)/36 = 4/36 = 1/9. Time needed = (2/3) ÷ (1/9) = (2/3)×9 = 6 days.

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