Answer: We can use the Pythagorean theorem to solve this problem. Let's call the length of the guy wire "x". Then we have a right triangle with legs of 4 and 20 (the distances from the pole to the stake and tower, respectively) and hypotenuse of x (the length of the guy wire). So we can write:
4^2 + 20^2 = x^2
Simplifying the left side, we get:
16 + 400 = x^2
416 = x^2
Taking the square root of both sides (and rounding to the nearest foot), we get:
x ≈ 20.4
Therefore, the length of the guy wire is approximately 20 feet.
Explanation: