Subject Area Lessons

## #39. Finding the Surface Area of a Sphere

Mathematics, level: Middle
Posted by Delbert Griffith (dgriffith@getonthe.net).
Sparta Middle School, Sparta, MO, US
Materials Required: paper, scissors, kickballs, rulers.
Activity Time: 2 classes (50-minute classes)
Concepts Taught: geometry, surface area

I first introduce the concept of "surface area" and we find the surface areas of rectangular prisms to get started. (This is prior to the actual lesson) I then ask students to predict the surface area of a sphere, and how one might find the surface area of a sphere. I then pass out an inexpensive kickball to each group, and newspaper. I tell the students to cut the several strips of paper into 1" by 4" strips. They are to then paste these strips onto the kickball, counting the number of strips used. By multiplying the number of strips by the area of each strip, the student can approximate the surface area of a sphere.

When this is done, i then have them find the radius of the kickball by rolling the ball on a tiled floor and measuring the distance from the starting point to the ending point of one complete revolution. We then get into a discussion and lecture on diameter and radius, and we develop formulas for finding the surface area of shperes. The kids really love it, and they retain this information very well! 