A and B complete a work in 5 days. A alone can do it in 10 days. If both together can do the work in how many days?
Pick one:
A) 3.33 days  B) 3.99 days  C) 2.99 days  D) 2.98 days  E) 2.44 days

Rationale: "1 / 5 + 1 / 10 = 3 / 10 10 / 3 = 3.33 days answer : a"
Answer: A