Answer: 16 men should be assigned to finish the work in 20 days.
Explanation:
Let's assume that the number of men needed to complete the work in 20 days is y. Then, the rate of work done by each man is given by 20/16=5/4 units of work per day.
So, the rate of work done by y men is given by 5/4 * y units of work per day.
Since the total work is constant, we have 20 men * 20/16 units of work per day = y men * 5/4 units of work per day.
Dividing both sides by 5/4, we get:
y = 20 * 20/16 / (5/4) = 20 * 4/5 = 16 men.
Therefore, 16 men should be assigned to finish the work in 20 days.