A man can do a piece of work in 5 days, but with the help of his son, he can do it in 3 days. In what time can the son do it alone?
Q1. A man can do a piece of work in 5 days, but with the help of his son, he can do it in 3 days. In what time can the son do it alone?
Answer: 7.5 days
Explanation: Son's rate = 1/3 − 1/5 = 2/15 per day, so the son alone takes 15/2 = 7.5 days.