Multiple choice

A can do a piece of work in 20 days, while B can do it in 12 days. B works for 9 days and then leaves. In how many days can A alone finish the remaining work?

  1. 3 days

  2. 5 days

  3. 7 days

  4. 11 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

A's rate = 1/20, B's rate = 1/12. B works for 9 days: 9/12 = 3/4 of work done. Remaining work = 1/4. A takes (1/4) / (1/20) = 5 days.

AI explanation

The total work is assumed as the lowest common multiple of 20 and 12, which is 60 units, meaning A's rate is 3 units per day and B's rate is 5 units per day. In 9 days of work, B completes 9 multiplied by 5 units, amounting to 45 units. This leaves 15 units of work remaining, which A can complete in 15 divided by 3 days, resulting in 5 days.

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