A and B together can do a piece of work in 10 days. B alone can finish it in 20 days. In how many days can A alone finish the work ?
Choose one
A) 10  B) 20  C) 21  D) 22  E) 23
Time taken by A to finish the work = XY/(Y-X)   = 10 x 20 / (20-10)   = 200/10= 
<gadget id="calculator">200/10</gadget>
<output>20</output>
20 days   ANSWER : OPTION 20
<result>B</result>
A and B together can do a piece of work in 10 days. B alone can finish it in 20 days. In how many days can A alone finish the work ?