15 beavers, working together in a constant pace, can build a dam in 4 hours. How many hours will it take 20 beavers that work at the same pace, to build the same dam? Choose the correct choice from the following answers.
A) 2 .	B) 4 .	C) 5 .	D) 6	E) 3 .

Rationale: "total work = 15 * 4 = 60 beaver hours 20 beaver * x = 60 beaver hours x = 60 / 20 = 3 answer : e"
Answer: E