Worker A takes 8 hours to do a job. Worker B takes 12 hours to do the same job. How long it take both A & B, working together but independently, to do the same job? Choices
A) 40 days	B) 24 / 5 days	C) 39 / 9 days	D) 30 / 9 days	E) 60 / 9 days

Rationale: "a ' s one hour work = 1 / 8 . b ' s one hour work = 1 / 12 . ( a + b ) ' s one hour work = 1 / 8 + 1 / 12 = 5 / 24 . both a & b can finish the work in 24 / 5 days b"
Answer: B