Answer: 19 ft
Explanation:
Hi, since the situation forms a right triangle (see attachment) we have to apply the Pythagorean Theorem:
c^2 = a^2 + b^2
Where c is the hypotenuse of the triangle (in this case the length of the ladder) and a and b are the other sides.
Replacing with the values given:
20^2 = (4 1/2)^2 + x^2
400=20.25 + x ^2
400-20.25 = x^2
379.75 = x^2
√379.75 = x
x = 19.48
x= 19 ft
Feel free to ask for more if needed or if you did not understand something.