Area and Perimeter Fun

Last week I introduced area and perimeter to my third graders.  It seemed like they were catching on when it came to rectangles and squares but they just were not getting the irregular shaped figures.  I ditched my regular plans and just went with an idea that popped into my head at the beginning of math.  It turned out to be awesome and the kids were eating it up!!



My BIG objective was to have the kids understand that the perimeter can change when the area remains the same. 



I first started the lesson by having the kids draw a 8x3 rectangle.  We talked about finding the area with the formula Length x Width.  They wrote the area under the figure.  The kids then counted the perimeter and wrote it.  They then drew a 6 x 4 rectangle and discovered that the perimeter was different!!  How did that happen?!  Finally they drew and irregular polygon with and area of 24. I just has the kids count out 24 squares.  They really had fun with this. Since everyone had a different shape, the kids worked with a partner to find each other's perimeter.  By this time they were fascinated!

 

After the kids learned that the perimeters change, I had them create four closed figures with the areas of 12 sq. cm, 20 sq. cm, 28 sq. cm, and 36 sq. cm.  I told them that at least two of these figures needed to be irregular shaped figures.  They were so excited!!  Once all the figures were drawn, they cut them out.

 

I put posters around the room and had the kids glue their figures on the correct posters.  Since I literally changed my plans at the last minutesand came up with this lesson, I had to hand write the words.  Next time I will create a title on the computer and glue it on each poster.  But it turned out well!  Tomorrow I PLAN to hang the posters around the room and have the kids visit each one to find the perimeters of each figure.  We might even have a contest to figure out which figure has the largest perimeter!  

This lesson was a perfect hands on lesson to teach area and perimeter!