A can do a job in 12 days and B can do it in 20 days. A and B working together will finish twice the amount of work in ------- days? Choose the correct choice from the following:
A) 15 days
B) 13 days
C) 22 days
D) 11 days
E) 19 days
15 days   1/12 + 1/20 = 2/15   15/2 *2= 
<gadget id="calculator">15/2 *2</gadget>
<output>15</output>
15 days
<result>A</result>
A can do a job in 12 days and B can do it in 20 days. A and B working together will finish twice the amount of work in ------- days?