A and B complete a work in 9 days. A alone can do it in 18 days. If both together can do the work in how many days?
Choose the correct choice from the following options
A) 6 days B) 8 days C) 5 days D) 7 days E) 15 days

Rationale: "1 / 9 + 1 / 18 = 1 / 6 6 / 1 = 6 days answer : a"
Answer: A