A does a work in 20 days and B does the same work in 30 days. In how many days they together will do the same work ?	Choose the correct choice from the following:
A) 5 days
B) 6 days
C) 9 days
D) 12 days
E) None of these
Explanation:   Firstly we will find 1 day work of both A and B, then by adding we can get collective days for them,   So,   A's 1 day work = 1/20   B's 1 day work = 1/30   (A+B)'s 1 day work =   (1/20+1/30)=1/12   So together they can complete work in 12 days.   Answer: 12 days
<result>D</result>
A does a work in 20 days and B does the same work in 30 days. In how many days they together will do the same work ?