x is 3 times as fast as y and working together , they can complete a work in 20 days . in how many days can y alone complete the work ? Choose the correct choice from the following.
A) 11 days	B) 80 days	C) 13 days	D) 15 days	E) 19 days

Rationale: x = 3 y x + y = 3 y + y = 4 y these 4 y people together can do the work in 20 days , which means y can alone do the work in 4 * 20 = 80 days . answer : b
Answer: B