Posted by **Mary** on Friday, September 30, 2011 at 3:56pm.

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?

- Algebra -
**Steve**, Friday, September 30, 2011 at 4:22pm
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

- For Steve - Algebra -
**Reiny**, Friday, September 30, 2011 at 4:53pm
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.

- Algebra -
**Steve**, Friday, September 30, 2011 at 5:27pm
cool. my bad

- Algebra -
**Steve**, Friday, September 30, 2011 at 5:28pm
In fact, i think I knew that, but got caught up in the heat of the explanation. :-(

- Algebra -
**karis**, Monday, October 3, 2011 at 11:11pm
what is the number whose distance is 5 to the left of 12

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