15 men take 21 days of 8 hrs. each to do a piece of work. How many days of 9 hrs. each would it take for 21 women if 3 women do as much work as 2 men? Choose the correct answer.
A) 30 B) 20 C) 19 D) 29 E) 39

Rationale: "let 1 man does 1 unit / hr of work 15 m in 21 days of 8 hrs will do ( 15 * 21 * 8 ) units 3 w = 2 m 1 w = ( 2 / 3 ) units / hr 21 w with 9 hrs a day will take ( 15 * 21 * 8 ) / ( 21 * 9 * ( 2 / 3 ) ) days = > 20 days answer : b"
Answer: B