Multiple choice

A and B can do a work in 12 days and 16 days respectively. They start working together, but after every 4th day A takes a day off and B works alone on that day. In how many days (integral value) will the work be completed?

  1. 9 days

  2. 8 days

  3. 13 days

  4. 14 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A's rate = 1/12, B's rate = 1/16. In 4 days, A+B do 4 * (1/12 + 1/16) = 4 * (7/48) = 7/12. On day 5, B works alone: 1/16. Total in 5 days = 7/12 + 1/16 = 31/48. This pattern continues until work is done.

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