A does a work in 10 days and B does the same work in 5 days. In how many days they together will do the same work ?  Choose the correct option:
A) 1/5
B) 2/7
C) 3/10
D) 3/11
E) 3/17
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 = 1/10   B's 1 day work = 1/15   (A+B)'s 1 day work =   (1/10+1/5)=(1+2/10)= 3/10   3/10
<result>C</result>
A does a work in 10 days and B does the same work in 5 days. In how many days they together will do the same work ?