A can do a job in 10 days and B can do it in 30 days. A and B working together will finish twice the amount of work in ------- days?	Choose the correct choice from the following:
A) 21 ½ days  B) 22 ½ days  C) 23 ½ days  D) 15 days  E) None of these
Explanation:   1/10 + 1/30 = 4/30 = 2/15   15/2 = 15/2 *2= 
<gadget id="calculator">15/2 *2</gadget>
<output>15</output>
15 days   Answer: 15 days
<result>D</result>
A can do a job in 10 days and B can do it in 30 days. A and B working together will finish twice the amount of work in ------- days?