A can do a work in 15 days and B in 20 days. If they work on it together for 3 days, then the fraction of the work that is left is	Choose the correct choice.
A) 8/17	B) 7/15	C) 3/15	D) 8/15	E) 13/20
Person ( A ) ( B ) ( A+B )   Time - ( 15 ) ( 20 ) (-)   Rate - ( 20 ) ( 15 ) ( 35 )   Work -(300) (300) (300)   therefore A+B requires (300/35) days to complete entire work   For 1st 4 days they work  35 * 3= 
<gadget id="calculator"> 35 * 3</gadget>
<output>105</output>
105   Remaining work is 300 - 105= 
<gadget id="calculator">300 - 105</gadget>
<output>195</output>
195   Remaining fraction of work is= 195/300 = 13/20   Answer 13/20
<result>E</result>
A can do a work in 15 days and B in 20 days. If they work on it together for 3 days, then the fraction of the work that is left is