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Stairs Slope

Find the slope of your stairs*.

First, take a ruler and measure the rise (the height) and the run (the part you step on) of your stairs**.

To fit the International Residential Code, the most your rise can be is 7.75 in. The smallest your run can be is 10 in. Do your stairs fall within this rule?

Example: At my house, the rise is 7.75 in. and the run is 10 in, so our stairs barely meet

the code.

Now, to find the slope of the line connecting the stairs, take the rise divided by the run.

Example: 7.75/10 = .775 or 77.5%. You can compare this to a 6% grade of a road, which means for every 100 feet forward, the road goes 6 ft up. My stairs are much steeper than a 6% grade road! Ask your child what a 100% grade would be. (The rise and run would be equal, meaning that if you went forward 100 ft, the road would go up 100 ft--a 45 angle).

**Measurement tips: Make sure that the student lines up the step with 0” on the ruler. Note that when measuring with inches, sometimes students confuse how many spaces there are in one inch. If the ruler is marked with eighths, there will be 9 lines from 0” to 1”.

Modify any parts of the task that are too hard or too easy. For example, younger children may need a ruler that shows only inches, and older children could use a ruler with sixteenths marked.

Task adapted from Lappan, et. al (2009). Moving straight ahead. Pearson (Connected Mathematics2 Curriculum).

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