To solve this question, we have to set up a proportion that relates the two triangles.
In the bigger triangle, the bottom piece equals 30 feet.
In the smaller triangle, the bottom piece equals 5 feet.
In the bigger triangle, the height equals x feet.
In the smaller triangle, the height equals 30 feet.
In a proportion, this would be:
5/30 = 30/x
To solve this proportion, we can use cross-products, or setting the products of the opposite numerators and denominators equal to each other.
5 * x = 30 * 30
Now we have to simplify both sides of the equation by completing the multiplication operations.
5x = 900
Finally, we must divide both sides by 5, to get the variable x alone on the left side of the equation (get rid of coefficient of 5)
x = 180
Therefore, x = 180 or the height of the bigger triangle (building) is 180 feet.