posted by Mary on .
A roof rises 2.3 feet vertically, and 7.4 feet horizontally. What is the grade of the roof?
I do not understand how to even find what the grade would be..can anyone help?
Ever heard of google? wikipedia?
You may have a calculator which allows you to switch among radians, degrees, and "grad" units. Guess what grads are? The grade.
On a highway you may see a sign near a steep hill, saying steep grade ahead: 6%.
The gradient is measured in vertical/horizontal, as a percent.
So, a 6% grade is one where the elevation changes 6' for every 100' of lateral distance.
So, a 100% grade is a 45° angle, because there is a rise of 1 unit for every horizontal unit.
Now, for your problem:
2.3/7.4 = 0.31 = 31% grade
The Grad on a calculator has nothing to do with the grade of a roof
The grade of a roof is simply the slope, which you found correctly.
In the DRG on a calcuator, the G stands for gradians, which was an attempt to make angles fit into the metric system.
A right angle is defined as 100 gradians.
you can test this by
setting your calcualtor to D and taking tan 45°
now set your calculator to G and take tan 50
you will get the same result.
Btw, I have yet to come across anybody who uses gradians in any calculation these days. They should be dropped from calclators.
cool. my bad
In fact, i think I knew that, but got caught up in the heat of the explanation. :-(
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