What is the perimeter, in cm, of quadrilateral ABCD if $AB \perp BC$, $DC \perp BC$, AB = 9 cm, DC = 4 cm, and BC = 12 cm?
If you draw it out , you will find AD = 13 cm 13 + 12 + 4 + 9 = 38 cm
AD = sqrt [ ( 5 - 0)^2 + (12 - 0)^2 ] = sqrt [ 25 + 144] =sqrt (169) = 13
So the perimeter = 9 + 12 + 4 + 13 = 38 units
+36916 
