if you know the square units of the house, and you find the factors, that is the different ways to place the house, ex. if you have a house that is 200 square units, and you get the factors, 200x1, 100x2, 50x4, 25x8, 20x10 5x40 then you have 6 ways, and if you turn the factors around you have another 6 ways, so there are 12 ways to put that house down.
