Adam is 40% more efficient than Blanc. How much time will they, working together, take to complete a job which Adam alone could have done in 20 days?	Pick one.
A) 35 days
B) 11 1â„3 days
C) 11 2â„3 days
D) 20 days
E) 11 3â„5 days
Ratio of times taken by Adam and Blanc = 100 : 140 = 5 : 7.   Suppose Blanc takes x days to do the work.   Then, 5 : 7 : : 20 : x â‡’ x = (20Ã—7)/5 â‡’ x = 28   Adamsâ€™s 1 dayâ€™s work = 1â„20; Blancâ€™s 1 days work = 1â„28   (Adam + Blanc)â€™s 1 dayâ€™s work = (1â„20 + 1â„28) = 3â„35   âˆ´ Adam and Blanc together can complete the job in 35â„3 days or 11 2â„3 days.   Answer 11 2â„3 days
<result>C</result>
Adam is 40% more efficient than Blanc. How much time will they, working together, take to complete a job which Adam alone could have done in 20 days?