A 20 foot ladder is leaning against the side of a building. The bottom of the ladder is 4 feet from the wall. How many feet above the ground does the ladder touch the wall?

It form a right triangle

legnth of ladder is hypotonuse

bottom of ladder from wall distance is one leg

distance up wall is other leg

a^2+b^2=c^2

c=hypotonuse and a and b are legs

4^2+b^2=20^2

16+b^2=400

minus 16 both sides

b^2=384

sqrt both sides

b=8√6 ft

aprox

b=19.59ft from ground