An office building casts a 90 foot shadow. at the same time of day, a 5 foot woman standing near the building casts an 8 foot shadow. what is the approximate height of the building to the nearest foot?

For this problem, you could use the Scale Factor.
I will use x for the height of the building.

So 8 is to 90 as 5 is to x.

Our equation is:

8(SF) = 90

Divide both side by 8:

SF = 45/4

Then, we plug SF into the next equation:

5(SF) = x
5(45/4) = x
56.25 = x

Round to the nearest foot, and the height of the building is 56 feet.