A and B can do a work in 12 days, B and C in 15 days, C and A in 20 days. How long will A, B, and C together take to do the work?
Q1. A and B can do a work in 12 days, B and C in 15 days, C and A in 20 days. How long will A, B, and C together take to do the work?
Answer: 10 days
Explanation: Rate of work for A+B = 1/12, B+C = 1/15, C+A = 1/20. Adding these gives 2(A+B+C) = 1/12 + 1/15 + 1/20 = 1/5, so A+B+C = 1/10.