Multiple choice

A and B together can complete a work in 12 days A alone can complete it in 20 days If B now does the work for half a day dally Then in how many days A and B together will complete the work?

  1. 15 days

  2. 20 days

  3. 45 days

  4. 30 days
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A and B together complete 1/12 of the work per day, while A alone completes 1/20. Therefore, B completes 1/30 per day. If B works for half a day daily, B contributes 1/60 daily, and A plus this contribution completes 1/15 per day, requiring 15 days.

AI explanation

Let the total work be the least common multiple of 12 and 20, which is 60 units. A completes 3 units per day and B completes 2 units per day, but if B works for half a day daily, B completes only 1 unit per day. Their new combined daily work becomes 4 units, so the total time to complete the 60 units of work is 60 divided by 4, which equals 15 days.

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