Answer
20 feet
Work Step by Step
The equation for finding the length of the sides of a right-angle triangle
$a^{2} + b^{2} = c^{2}$
Substitute in the known lengths
$12^{2} + 16^{2} = c^{2}$
Square and add the numbers
$144 + 256 = c^{2} = 400$
Find the square root to get the length of the hypotenuse
$c = \sqrt 400 = 20$
