A person decided to build a house in 100days. He employed 100men in the beginning and 100 more after 10 days and completed the construction in stipulated time. If he had not employed the additional men , how many days behind schedule would it have been finished? Choose the most appropriate option.
A) 40  B) 80  C) 70  D) 60  E) 90

Rationale: "200 men do the rest of the work in 100 - 10 = 90 days 100 men can do the rest of the work in 90 * 200 / 100 = 180 days required number of days = 180 - 90 = 90 days answer is e"
Answer: E