Multiple choice

A and B can paint a fence in 10 days and 15 days, respectively. They work together for 4 days, and then A leaves. How many more days will it take for B to finish painting the fence?

  1. 5 days

  2. 7 days

  3. 8 days

  4. 9 days

  5. 10 days
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

A's rate is 1/10 and B's rate is 1/15. Together, they work at (1/10 + 1/15) = 1/6 of the fence per day. In 4 days, they complete 4/6 = 2/3 of the fence, leaving 1/3 to be finished by B. Since B paints 1/15 per day, it takes B (1/3) / (1/15) = 5 days to finish.

AI explanation

Using the LCM method, let the total work be 30 units, so the daily work rates of A and B are 3 and 2 units respectively. Working together for 4 days, they complete 4 * (3 + 2) = 20 units, leaving 30 - 20 = 10 units of work remaining. B works alone at 2 units per day to finish the rest, requiring 10 / 2 = 5 more days.

Keep practicing — related questions