Your calculation for the cylinder volume is 31,792.50 cubic feet
I calculate it as 31,808.63 cubic feet
So, the 10,000 cubic feet mark would be located at
(10,000 / 31,808.63) * 45 feet =
0.3143800912
* 45 =
14.147104104
from the bottom
45 -
14.147104104
=
30.852895896
from the top
and that rounds to 31 feet
I get the same answer as you.
