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

Let b bricks:

b = 400, let H height and l length

Area = 81*31 or 6.75*2.58 = 17.44 ft²

b (17.44ft²) = Hl

400 (17.44 ft²) = 42 l

l = 6975/42 = 166.07

so the length of the wall is 166 ft approximately as a whole number