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Grade: Middle
Subject: Mathematics

#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 (
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


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 youre 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 Diameter.

7. Combine the class data.

8. Now peel you orange and fit the peelings into the circles. ** Dont lose any**

9. Record your findings.

10. Discuss results.

C = 2r
S.A. = 4r2