A group of men decided to do a work in 20 days, but 10 of them became absent. If the rest of the group did the work in 40 days, Find the original number of men?
Choices:
A) 20 B) 50 C) 40 D) 100 E) 25

Rationale: "original number of men = 10 * 40 / ( 40 - 20 ) = 20 answer is a"
Answer: A