an apartment building has the same number of units on each floor. the building has 5 times as many units per floor as number of floors and there are 405 units total. how many floors does the building have?

Question

anonymous · Answer

f=number of floors
u=number of units per floor
f*u=405
5f=u          <- since there are 5 times more units per floor than floors

subsitute equation 2 into equation 1
f*5f=405
$$5f ^{2}$$=405
$$f ^{2}$$=81
f=9