Multiple choice

$A$ and $B$ together can do a piece of work in 8 days. $B$ alone can do it in 12 days. $B$ alone works at it for 4 days. In how many more days after that could $A$ alone complete it.

  1. 15 days

  2. 18 days

  3. 16 days

  4. 20 days
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

If A+B do the work in 8 days and B in 12 days, A's rate is 1/8 - 1/12 = 1/24 of the work per day. B works for 4 days, completing 4/12 = 1/3 of the work, leaving 2/3 of the work for A. A completes the remaining 2/3 at a rate of 1/24, taking (2/3) * 24 = 16 days.

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