First we need to find how far away the base of the ladder is from what it is leaning against. The ramp is the hypotenuse and the height from the ground in a leg. Let’s use Pythagorean’s theorem.
a^2 + b^2 = c^2
Substitute
a^2 + (5)^2 = (20)^2
Solve for a^2
a^2 = (20)^2 - (5)^2
Solve for a
a = 5 √15
The slope will be rise over run
5/5 √15 = √15/15 or 0.258…
