A and B together can complete a piece of work in 4 days. If A alone can complete the same work in 12 days, in how many days can B alone complete that work?  Choose the correct choice from the following answers
A) 22 days
B) 4 days
C) 13 days
D) 6 days
E) 9 days
(A + B)'s 1 day's work = (1/4). A's 1 day's work = (1/12).   B's 1 day's work =((1/4)-(1/12))=(1/6)   Hence, B alone can complete the work in 6 days.   Answer is 6 days.
<result>D</result>
A and B together can complete a piece of work in 4 days. If A alone can complete the same work in 12 days, in how many days can B alone complete that work?