81 x 31 = 2 511 (area of a brick)
2511 x 400 = 1 004 400 (area of the wall)
Convert 1 004 400" to ft. [1ft. = 12"]
1 004 400 / 12 = 83 700 ft.
Now this is what we have.
-Hight 42 ft.
-Length X ft.
-Area 83 700ft.
Algebra time.
42 x X = 83 700 (to get X you would devide 83 700 by 42)
83 700 / 42 = 1 992.85ft. (X = 1 992.85ft.)
So the length of the wall would be 1992.85ft.
