Resources and Tools for Elementary Math Specialists and Teachers

Perimeter and Area

This discussion is part of a collection:Measurement

Many students have difficulty distinguishing between these two measures. Yes we know that we can remind a learner to see the word rim in perimeter and area is how much space we have. But there is confusion. What instructional strategies have you used in the classroom for learners to have a clear understanding?

Replies

Is there an appropriate time in K-5 to differentiate between a triangle (as just the three connected segments) versus a triangular region? Perhaps some of the issues children have distinguishing between perimeter and area would be clarified if we treated 2-D shapes as not including their interior regions at some point.

This is a good example of the need to press for precise use of mathematical language often and not fall into informal usage all the time. The area of a circle is zero, but the area of a circular region is pi x r x r.

My strategy is to never jump right to a formula. An index card has P = 3 + 5 + 3 + 5 inches. Let the student construct the shortcut. For areas, cover or color the region and study many examples tied to an investigation like fixed perimeter/max area.

There is a really great video in this catalog from teacher Suney Park, the video is called "Table for 22: A Real-World Geometry Project", this video puts these terms into a context that gives it meaning. I highly recommend that you check out this video and try this in your classroom! This resource is also listed in the Classroom collection for measurement Grade 3-5.

Table for 22 is also a great example of incorporating the CCSS practice standards and the NCTM process standards! If you're looking for a video that you can use to show teachers how these standards look "in action" in the classroom, look at Table for 22.