Perimeter Formulas- Rectangles

When I started planning out lessons to teach the perimeter and area of a rectangle in fourth grade, I thought it would be a simple concept. The students should have learned about perimeter and area in depth in third grade, so I figured this would just be a review. Boy, was I wrong!

In fourth grade, this standard (4.MD.A.3) goes way beyond just being able to add or multiply. It's one of their first introductions to using formulas. The formula for the area of a rectangle is pretty straightforward (length x width), but what about perimeter? Is it length + length + width + width? Or 2 x length + 2 x width? Or, maybe it's 2 x (length + width)?

This can all be pretty confusing for a fourth grader just being exposed to formulas. In my opinion, it's best to start with the formula for the area of a rectangle (instead of perimeter), as it really is more of a review of what students learned in third grade. The perimeter formulas can be trickier.

As with all tricky, complicated concepts, true understanding takes time, but is also completely necessary in order for students to be able to apply that understanding. Lots of good discussion and problem solving is necessary for kids to be able to bump up against the edges of what they think they know, and the question and consolidate their ideas from there.

To help out with this deceptively complex topic, here's a free, printable practice page. Just click here to get these rectangle perimeter formula problems.

Happy (Perimeter Formula) Teaching !!