Multiple choice

A and B can together finish a work in 30 days. They worked together for 20 days and then B left. After another 20 days, A finished the remaining work. In how many days A alone can finish the job?

  1. 50

  2. 60

  3. 48

  4. 54
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A+B = 1/30. In 20 days, they do 20/30 = 2/3 of the work. Remaining work = 1/3. A finished this in 20 days. So A's rate = (1/3) / 20 = 1/60. A alone takes 60 days.

AI explanation

Let A and B's one day work be 1/30, so their combined work for 20 days is 20/30 or 2/3 of the task. The remaining 1/3 of the task is completed by A alone in 20 days. Using the basic work formula, if A takes 20 days for 1/3 of the work, A takes 60 days to complete the entire job alone.

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