Student: A and B can do a work in 12 days, B and C in 30 days and C and A in 36 days. In how many days will the work be completed, if all three of them work together?\nOptions:\n(A) 180/63 days\n(B) 160/13 days\n(C) 180/13 days\n(D) 680/13 days\n(E) 180/63 days.
Another student: Let's say, hmmm...

User
One day work of A and B = 1/12\nOne day work of B and C = 1/30\nOne day work of C and A = 1/36\n2(A + B + C) = 1/12 + 1/30 + 1/36\n2(A + B + C) = 13/90\n(A + B + C) = 13/180\nNumber of days required = 180/13 days. Final answer: (C).
Assistant