#4013. Proving Formula for the Surface Area of a Sphere

Mathematics, level: Middle
Posted Tue Jun 5 17:51:07 PDT 2007 by Louise Mullane (lmullane@staff.ednet.ns.ca).
Graham Creighton Junior High, Nova Scotia, Canada
Materials Required: Oranges, String, Knife, Paper, Pencil, Ruler, Calculator, and class list.
Activity Time: one hour
Concepts Taught: Geometry

Materials:

Oranges, String, Knife, Paper, Pencil (or pen), ruler, calculator, and class list.

1. Estimate the surface area of your orange and explain your reasoning.

2. With your string measure around you¡¯re orange and record your data.

3. Using a knife ¨C cut your orange in half.

4. Place half of your orange upside down on the paper, and trace the orange 6 times ¨C without overlapping.

5. In the first circle measure the diameter.

6. On your chart next to your name write in the circumference, the diameter, and calculate the last column ¨C Circumference ¡Â Diameter.

7. Combine the class data.

8. Now peel you orange and fit the peelings into the circles. ** Don¡¯t lose any**

9. Record your findings.

10. Discuss results.

C = 2¦Ðr
S.A. = 4¦Ðr2