An extension ladder is leaned against a wall and does not extend past the top of the wall. The top of the ladder touches the wall at a point 20′ above grade. What is the minimum distance the foot of the ladder must be from the wall?

An extension ladder is leaned against a wall and does not extend past the top of the wall. The top of the ladder touches the wall at a point 20′ above grade. What is the minimum distance the foot of the ladder must be from the wall?