A can do a half of certain work in 70 days and B one third of the same in 35 days. They together will do the whole work in?
Pick one.
A) 1 / 65 B) 1 / 62 C) 1 / 63 D) 1 / 60 E) 1 / 61

Rationale: a = 140 days b = 105 days 1 / 140 + 1 / 105 = 7 / 420 = 1 / 60 = > 60 days answer : d
Answer: D