36 men can complete a piece of work in 18 days. In how many days will 9 men complete the same work ? Pick one:
A) 24  B) 77  C) 88  D) 72  E) 21

Rationale: "explanation : less men , means more days { indirect proportion } let the number of days be x then , 9 : 36 : : 18 : x x = 72 answer : d ) 72 days"
Answer: D