Geoboards have many uses. One is teaching perimeter and area. Here is a fun activity we enjoy for teaching perimeter and area with geoboards.
Teaching Perimeter with Geoboards
1. Instruct your student to assume that the line connecting two pegs on the geoboard equals “1 length” for this activity. For the purpose of this beginning perimeter activity, we will ignore the fact that the length of diagonal lines between pegs is longer than transverse or longitudinal lines and regard the length between two adjacent pegs as “1 length.”
2. Have your student place a rubber band around some pegs. Explain that perimeter is the distance around the outer boundary of a two-dimensional shape. This video is excellent in explaining this concept, but I disagree on one point. Multiplication is not repeated addition. (Denise Gaskins explores this in more detail.)
3. To calculate the perimeter, add the lengths of all the sides of the shape. Ask your student to calculate the perimeter of the resulting shape. Some examples are shown below.
(Optional) Instead of using rubber bands with the geoboards, you could use kinetic sand.
Instead of placing rubber bands around the geoboard pegs, have your child draw shapes with a popsicle stick by connecting the dots. Calculate perimeter in the same manner as described above.
Teaching Area with Geoboards
1. Instruct your student to assume that one square on the geoboard equals “1 square” for this activity.
2. Have your student place a rubber band around some pegs. Explain that area is the size of a surface or the amount of space inside of a two-dimensional shape. Here’s a video that explains area.
3. To calculate the area, multiply the length of the shape by the width. Ask your student to calculate the area of the resulting shape. Some examples are shown below.
3. You can also use geoboards to explain how to find the area of a triangle. The formula to determine the area of a triangle is 1/2 x base x height. The video above explains why this formula works (the explanation begins at 4 min 45 seconds). Here is an example of finding the area of a triangle on the geoboard.
4. Once you know how to find the area of a triangle, you can find the area of any straight-sided shape. See the examples below.
(Optional) Instead of using rubber bands with the geoboards, you could use kinetic sand. See instructions above in the perimeter section.
Find more math manipulative and game suggestions in the math manipulative post series.
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