A work as fast as B. If B can complete a work in 36days independently,the number of days in which A and B can together finish the work in?	Pick one: A) 12 days B) 3 days C) 4 days D) 5 days E) 6 days

Rationale: "ratio of rates of working of a and b = 2 : 1 ratio of times taken = 1 : 2 a ' s 1 day work = 1 / 18 b ' s 1 day work = 1 / 36 a + b 1 day work = 1 / 18 + 1 / 36 = 3 / 36 = 1 / 12 a and b can finish the work in 12 days answer is a"
Answer: A