X does a work in 20 days. Y does the same work in 40 days. In how many days they together will do the same work?  Choose the most appropriate option
A) 10	B) 12	C) 20	D) 30	E) 13.33
X's 1day's work= 1/20   Y's 1 day's work=1/40   (X+Y)'s 1day's work= (1/20+1/40)=1/13.33   both together will finish the work in 13.33 days.   correct option is 13.33
<result>E</result>
X does a work in 20 days. Y does the same work in 40 days. In how many days they together will do the same work?