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? Choose one:
A) 180/18
B) 180/15
C) 180/13
D) 180/12
E) 180/11
One day work of A and B = 1/12   One day work of B and C = 1/30   One day work of C and A = 1/36   2(A + B + C) = 1/12 + 1/30 + 1/36   2(A + B + C) = 13/90   (A + B + C) = 13/180   Number of days required = 180/13 days.   Answer: 180/13
<result>C</result>
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?