Multiple choice

A can do a piece of work in 12 days and B alone can do it in 16 days. They worked together on it for 3 days and then. A left. how long B take to finish the remaning work?

  1. $8$ days
  2. $5$ days
  3. $7$ days
  4. $9$ days
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

A's rate = 1/12, B's rate = 1/16. Combined rate = 1/12 + 1/16 = 7/48. In 3 days, they do 3 * (7/48) = 21/48 = 7/16 of the work. Remaining work = 1 - 7/16 = 9/16. B takes (9/16) / (1/16) = 9 days to finish.

AI explanation

A and B together complete 1 divided by 12 plus 1 divided by 16 of the work per day, which equals 4 divided by 48 plus 3 divided by 48 equals 7 divided by 48. In 3 days, they finish 3 times 7 divided by 48, which equals 7 divided of 16, leaving 1 minus 7 divided by 16 equals 9 divided by 16 of the work remaining. Since B alone completes 1 divided by 16 of the work per day, B requires (9 divided by 16) divided by (1 divided by 16) days to finish the remaining work, which equals 9 days.

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