A can do a piece of work in 30 days. He works at it for 5 days and then B finishes it in 20 days. In what time can A and B together it? Choices
A) 14 1/7 days  B) 15 1/7 days  C) 16 2/3 days  D) 17 1/7 days  E) 18 1/7 days
5/10 + 20/x = 1   x = 40   1/30 + 1/40 = 7/120   120/7 = 17 1/7 days   ANSWER:17 1/7 days
<result>D</result>
A can do a piece of work in 30 days. He works at it for 5 days and then B finishes it in 20 days. In what time can A and B together it?