Multiple choice

A can do a piece of work in 10 days and B can do the same piece of work in 20 days. They start the work together; but after 5 days, A leaves. In how many days will B do the remaining work?

  1. 5 days

  2. 6 days

  3. 8 days

  4. 10 days
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A's rate = 1/10, B's rate = 1/20. Together = 3/20. In 5 days, they do 5 * (3/20) = 15/20 = 3/4 work. Remaining work = 1/4. B does 1/4 work at rate 1/20 in (1/4)/(1/20) = 5 days.

AI explanation

Using the least common multiple method, let the total work be 20 units, so the daily work of A is 2 units and the daily work of B is 1 unit. Working together for 5 days, they complete 3 units per day for a total of 15 units, leaving 5 units of work to be done. Since B works alone at a rate of 1 unit per day, B will finish the remaining 5 units in 5 days.

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