If 5 men can complete a work in 20 days, how many men are required to complete the same work in 10 days?
Answer: A. 10 men
If 5 men can complete the work in 20 days, the total work is 5 * 20 = 100 man-days. To complete it in 10 days, 100 man-days / 10 days = 10 men are required.