Multiple choice

X takes 15 days to do a job. He works on it for 3 days and then, Y alone finishes the remaining job in 8 days. In how much time will X and Y finish the job, if they work together?

  1. 4 days

  2. 6 days

  3. 30 days

  4. 10 days

  5. 5 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

X does 1/15 of the job per day. In 3 days, X does 3/15 = 1/5 of the job. Remaining job is 4/5, which Y finishes in 8 days, so Y's rate is (4/5) / 8 = 1/10 per day. Combined rate is 1/15 + 1/10 = 5/30 = 1/6, so they take 6 days together.

AI explanation

In 3 days, X completes 3/15 or 1/5 of the job, leaving 4/5 of the work for Y to finish in 8 days. This means Y requires 8 * 5/4 = 10 days to complete the entire job alone. Working together, their combined one-day work is 1/15 + 1/10 = 1/6, meaning they will finish the job in 6 days.

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