First find the operating cost for 1 acre. Find that by dividing $551,520 by 20 acres. That gives us $27,576 per acre. Now we can set up a proportion to solve for the number of acres that have an operating cost of $441,216:
Cross multiply to get:
27576x = 441216 so
x = 16
We did not have to find the cost per acre to solve this. We could have set up the proportion with $551,520 on the top of the ratio and 20 on the bottom and we would still have gotten the same answer. I just figured the numbers wouldn't be as large if we divided to find the cost per unit.