A can do a piece of work in 10 days and B alone can do it in 20 days. How much time will both take to finish the work ?	Pick:	A) 5.333	B) 6	C) 6.666	D) 8.333	E) 9

Rationale: "this question can be solved by different methods . we need to conserve time in exams so solving this problem using equations is the good idea . time taken to finish the job = xy / ( x + y ) = 10 x 20 / ( 10 + 20 ) = 200 / 30 = 6.666 days answer : c"
Answer: C