A and B can complete a work in 12 and 15 days respectively. They start working together but A leaves 4 days before completion. In how many days is the work completed?
Q1. A and B can complete a work in 12 and 15 days respectively. They start working together but A leaves 4 days before completion. In how many days is the work completed?
Answer: 9 days
Explanation: Let's denote total work as 1. A's 1 day work = 1 / 12, B's = 1 / 15. Together, they do 1 / 12 + 1 / 15 = 9 / 60 = 3 / 20 per day.