In my geometry classes, I have been teaching my students about geometric solids- prisms, cylinders, cubes, cones, spheres, pyramids. Yesterday we learned that the surface area of a sphere is 4 times the area of a circle with the same radius. My students asked why it was 4 and not 3 or 5 or 7. I told them to wait...until today! I bought a bunch of oranges and brought them into class this morning. Each group of students got a tape measure to estimate the circumference of their orange and then find their radius. I instructed them to construct 6 circles with that same radius on a sheet of paper. Then we peeled our oranges (and made my classroom smell great in the process!).
I told the students were were going to fill our circles with peel. They made predictions on how many circles should be filled with the orange peels and then started filling the circles. The point of the activity is to provide a more tactile example of why it is 4 times the area of a circle and not 3 or 5 or 7. By the end of the class, some of my students gave me great "ah-ha moments" when they realized what we were doing. Great activity for geometry students! (especially ESL students...)
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