A can do a job in 30days and B in 40days. If they work on it together for 10 days, then the fraction of the work that is left is?  Select:
A) 2/11
B) 3/13
C) 5/12
D) 7/10
E) 6/15
A's 1 day work = 1/30   B's 1day work = 1/40   A+B 1day work = 1/30 + 1/40  +  1= 
<gadget id="calculator"> +  1</gadget>
<output>1</output>
1/30 + 1/40= 7/120   A+B 4days work = 7/120*10 = 7/12   Remaining work = 1 - 7/12 = 5/12   Answer is 5/12
<result>C</result>
A can do a job in 30days and B in 40days. If they work on it together for 10 days, then the fraction of the work that is left is?