The Angle of a Ramp

US accessibility rules limit a wheelchair ramp to a rise of 1 for every 12 along the ground. Rise and run are the two legs, so the angle comes from arctan, and one decimal place is enough to compare it with the limit.

A ramp that rises 0.6 m over 9 m of run has $\tan\left(\theta\right) = \frac{0.6}{9}$. arctan gives about 3.814°, and to one decimal place that is 3.8°. The second decimal tells you whether the first goes up: here it is 1, so it stays.