Fred is safety conscious. he knows that to be safe, the distance between the foot of the ladder and the wall should be 1/4 the height of the wall, fred needs to get on the roof of the school building which is 20 ft tall. how long should the ladder be if he wants it to rest on the edge of the roof and meet safety standards? round your answer to the nearest tenth.

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:

and

and

so

c = 20.6 ft