A telephone pole is 45 feet tall and casts a 20 foot shadow. A street lamp next to the
telephone pole casts a 12 foot shadow.
Calculate the height of the street lamp.

Create a proportion for this problem.

45 feet pole. x
——————- = ——————
20 foot shadow. 12 foot shadow

Cross multiply.

20x = 540

Divide both sides by 20 to isolate x.

x = 27

The height of the street lamp is 27 feet tall.