A and B together finish work in 12 days. A alone takes 20 days. How long does B alone take?
Q1. A and B together finish work in 12 days. A alone takes 20 days. How long does B alone take?
Answer: 30 days
Explanation: B's one day work is 1/12 minus 1/20, which is 1/30. So B alone needs 30 days.