Section 1

Read more about how road grade is calculated on page 25 of Mathworks 11. Begin at “Explore the Math.” As you read, think about these questions:

• If the slope of a roof is referred to as pitch, then what is the slope of a road referred to as?
  
  
• What is the one small difference between the slope formula and the percent grade formula?

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Using an appropriate grade is not just important with roads. The comfort and safety of athletes can be affected by the way their playing fields are constructed. Playing fields of grass need a crown (high point) in the middle and should slope to the edges. The slope needs to be between 2.0% and 2.5% for the grass field to drain well.

 

Example

 

A Canadian football field is typically 65 yd wide. If the crown in the centre is 3 ft high, would the field meet the requirements for good drainage?

 

 

The crown of the field will be in the centre. That is half the width of 65 yd. As the illustration shows, this is 32.5 yd from the sidelines.

 

Remember to have the rise and run in the same units when calculating both slope and percent grade.

 

You may remember that 1 yd is equivalent to 3 ft. So the crown is 3 ft high or 1 yd high. Now that all measurements are in yards, finding the percent grade is simpler.

 

A crown of 3 ft would exceed the 2% to 2.5% range needed to have the field drain adequately.