A can do a job in 20 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.
A) 24 days  B) 22 ½ days  C) 23 ½ days  D) 12 ½ days  E) None of these
Explanation:   1/20 + 1/30 = 5/60 = 1/12   12 = 12 *2= 
<gadget id="calculator">12 *2</gadget>
<output>24</output>
24 days   24 daysnswer: 24 days
<result>A</result>
A can do a job in 20 days and B can do it in 30 days. A and B working together will finish twice the amount of work in ------- days?