Answer:
Step-by-step explanation:
This is a right triangle problem using Pythagorean's Theorem. The height of the building to the edge of the roof is 20 feet. If the ladder has to be 1/4 the height of the wall away from the building, then the base of the right triangle is 1/4 of 20 which is 5 feet. The ladder itself is the hypotenuse of the triangle, for which we are seeking a length. Use Pythagorean's Theorem:
[tex]c^2=20^2+5^2[/tex] and
[tex]c^2=400+25[/tex] and
[tex]c^2=425[/tex] so
c = 20.6 ft