Posted by **anna** on Monday, March 10, 2008 at 8:51pm.

The grade of a road is 7%. What angle does the road make with the horizontal?

I'm confused!! What is the grade of a road? Thanks for the help!

- geometrey -
**drwls**, Monday, March 10, 2008 at 8:58pm
The "grade" is the tangent of the slope angle.

arctan 0.07 = 4.00 degrees

(4 degrees is the angle whose tangent is 0.07)

- geometrey -
**drwls**, Monday, March 10, 2008 at 9:05pm
I used the arctan key of my hand calculator. If you don't have one, you should use a table of trig functions

- geometrey -
**drwls**, Tuesday, March 11, 2008 at 8:29am
The answer to your second question is the tangent of 8 degrees. That is 0.1405, for a 14.05% grade.

You don't find many roads that steep. Driveways, maybe.

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