A can do a job in 15days and B in 20days. If they work on it together for 8 days, then the fraction of the work that is left is?  Pick
A) 2 / 15	B) 8 / 15	C) 3 / 11	D) 1 / 12	E) 1 / 15

Rationale: "a ' s 1 day work = 1 / 15 b ' s 1 day work = 1 / 20 a + b 1 day work = 1 / 15 + 1 / 20 = 7 / 60 a + b 8 days work = 7 / 60 * 8 = 14 / 15 remaining work = 1 - 14 / 15 = 1 / 15 answer is e"
Answer: E