A, B and C can do a piece of work in 24 days, 30 days and 40 days respectively. They began the work together but C left 12 days before the completion of the work. In how many days was the work completed?  Choose the most appropriate option:
A) 13 days  B) 16 days  C) 18 days  D) 11 days  E) 38 days
One day work of A, B and C = 1/24 + 1/30 + 1/40 = 1/10 Work done by A and B together in the last 12 days = 12*(1/24 + 1/30) = 9/10   Remaining work = 1/10   The number of days required for this initial work = 1 days.   The total number of days required = 12 + 1= 
<gadget id="calculator">12 + 1</gadget>
<output>13</output>
13 days.   13 daysnswer: 13 days
<result>A</result>
A, B and C can do a piece of work in 24 days, 30 days and 40 days respectively. They began the work together but C left 12 days before the completion of the work. In how many days was the work completed?