Two flagpoles stand side by side. The first flagpole is 50 feet tall. The second flagpole is as tall as the first flagpole's shadow is long. The second flagpole's shadow is 18 feet long. How many feet tall is the second flagpole?

50 / x = x / 18

Multiply both sides of the equation by 18 .

900 / x = x

Multiply both sides by x .

900 = x^{2}

Take the positive, since x is the height of a flagpole, square root of both sides.

30 = x

The second flagpole is 30 ft tall.