Worker A takes 4 hours to do a job. Worker B takes 10 hours to do the same job. How long it take both A & B, working together but independently, to do the same job?	Answers
A) 20 / 9 B) 40 / 9 C) 40 / 14 D) 60 / 9 E) 80 / 9

Rationale: one day work of a = 1 / 4 one day work of b = 1 / 10 so one day work of a and b together = 1 / 4 + 1 / 10 = 14 / 40 so total days required = 40 / 14 answer : c
Answer: C