I love a good hands on activity that helps my students remember the math they are learning. A great activity to remember the surface area of a sphere formula is to investigate the surface area of an orange.
Make sure to use oranges instead of clementines as the clementines are not as spherical as oranges. Students trace the outline of an orange onto a piece of paper, keeping their pencil perpendicular to the paper as best they can. Then have students use a compass to copy the same size circle several more times on their paper. Ask students to make a conjecture about how many circles they believe the orange peel will cover once they have peeled the orange.
Once students have their circles and conjecture, it is time to peel the orange. Students peel the orange and then test out their conjectures by covering each circle, one at a time. Students should find that the orange peel is able to cover 4 circles. Then as a class, make the connection between the radius of a circle and the radius of a sphere, like an orange. Ask students to write a formula for the surface area of their orange.
If you would like to grab a free copy of my Surface Area Investigation Activity, here is the link:
Alternate Ways to Facilitate this Activity:
- Each student completes the activity on their own(an orange for each student)
- Students work in groups of 3 or 4 students (7-10 oranges)
- Teacher has student volunteers go to the front of the room to model the activity for the class (1 orange)