If 400 bricks, each measuring 81" by 31", are required to build a wall 42 feet high, how long is the wall?

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.