CAS with Percentages

As I think about important skills for students, percentages stand out to me as an important skill for both elementary and middle school students that is not understood completely.  The students memorize the algorithms we set before them but never really reach the mathematical understanding of why and how we use them.  Using the TI-Nspire CX CAS handheld and some teacher preparation, students can delve into the why’s and how’s of percentages.  For example, start the lesson by putting the following slide on the board or send to student handhelds.

Percent Pic 1

Ask students the following questions:

  • What stays the same?
  • What changes?
  • Why do you think the last one is false?

Using a Quick Poll in the TI Navigator system or a cooperative learning strategy, facilitate student discussions on their answers.  The students can use their devices to investigate other percentages to see if their theories hold true. Teachers can use the activity Solving Percent Problems from the TI Math Nspired website as a follow up activity or intro activity for the lesson on using percents to solve problems.  As the unit progresses other investigations and discussion starters could look like this:

Percent Pic 3

Ask questions like, “What do you notice about the numbers?”, “What is the relationship between the numbers?”, “What conclusion can you make based on this pattern?”.  Also show some other percentages such as the slide below asking similar questions.

Percent pic 2


Of course as in any good unit of study, opportunities for practice and hands-on applications are needed throughout the unit to master the skill but getting students motivated to understand the math is the first step.  Investigations such as these will allow students to delve deeper into the math instead of skimming the surface with algorithms only.

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