Is this question asking for descriptions?
Suppose

At the same time, we can write

Note that
(just reverse the sum). Let's pair the first terms of
and
, and the second, and the third, and so on:

Now, each grouped term in the sum on the right side adds to 151. There are 52 grouped terms on that same side (because there are 50 numbers in the range of integers 51-100, plus 50 and 101), which menas

But
, as we pointed out, so

Answer:
254 4/7 or 254.34 ft² (it depends on which method you use.)
Step-by-step explanation:
To find the area of a circle, the formula is πr².
I'll use both 22/7 and 3.14 as pi, so I'll end up with two different answers. Just choose the more reliable one.
22/7 version:
22/7 * 9^2
22/7 * 81/1
1782/7
254 4/7 ft²
3.14 version:
3.14 * 9^2
3.14 * 81
314 - (3.14 * 19)
314 - 62.8 + 3.14
251.2 + 3.14
254.34 ft²
As I said, I ended up with two different answers. You also had said not to round my answer, so the 22/7 version has a mixed number.