Question

A hill that has a 31.7% grade is one that rises 31.7 m vertically for every 100.0 m of distance in the horizontal direction. At what angle is such a hill inclined above the horizontal

Answer 1

The grade is also the tangent of the angle above horizontal.

The angle whose tangent is 0.317 is called the "arctangent" of 0.317

It's 17.6 degrees.