A can do a job in 20 days and B can do it in 30 days. A and B working together will finish thrice the amount of work in ------- days?  Choose the most appropriate option:
A) 22 days  B) 22 days  C) 36 days  D) 72 days  E) 24 days
1/20 + 1/30 =5/60 = 1/12   12/1= 
<gadget id="calculator">12/1</gadget>
<output>12</output>
12 *3= 
<gadget id="calculator">12 *3</gadget>
<output>36</output>
36 days   Answer: 36 days
<result>C</result>
A can do a job in 20 days and B can do it in 30 days. A and B working together will finish thrice the amount of work in ------- days?