Multiple choice

A can complete a piece of work in 12 days, while B can complete the same work in 18 days. They start working together, but A leaves the work 3 days before its completion. In how many total days is the work finished?

  1. 8 days

  2. 9 days

  3. 7.5 days

  4. 6 days

  5. 8.4 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Let total work be 36 units. A does 3 units/day, B does 2 units/day. Let total days be x. B works for x days, A works for x-3 days. 3(x-3) + 2x = 36. 3x - 9 + 2x = 36. 5x = 45. x = 9 days.

AI explanation

Let the total work be the least common multiple of 12 and 18, which is 36 units, so A does 3 units per day and B does 2 units per day. Since A leaves 3 days before completion, B works alone for the final 3 days to complete 3 * 2 = 6 units. The remaining 30 units were done by A and B together at a rate of 5 units per day, taking 6 days. The total time taken to finish the work is 6 days plus 3 days, which equals 9 days.

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