R and S together can plough a field in 10 hours but by himself R requires 15 hours. How long would S take to plough the same field? Choose the most appropriate option:
A) 24hours	B) 5 hours	C) 10hours	D) 15hours	E) 20hours
f R and S together can do a piece of work in x days and R alone can do the same work in y days, then S alone can do the same work in x y/ y â€“ x days.   the No. of hours required by S= 10 Ã— 20/ 20 â€“ 10 = 200/10= 
<gadget id="calculator">200/10</gadget>
<output>20</output>
20 hours   20hours
<result>E</result>
R and S together can plough a field in 10 hours but by himself R requires 15 hours. How long would S take to plough the same field?