# Interactive video lesson plan for: How to calculate the area of a circle, plus simple proof for the formula

#### Activity overview:

The formula for the area of a circle is A = pi x r^2, or pi times r squared (radius squared). I show how to use the formula in several example situations. We then solve a few word problems. Lastly, I show a simple proof for the formula, based on dividing the circle into many sectors, which are close to triangles. Rearranging those sectors, we get a shape that is close to a parallelogram. Starting from the area of the parallelogram, we get the familiar formula for the area of a circle.

This lesson is meant for 7th grade math or for pre-algebra. Check out also my other pre-algebra videos at http://www.mathmammoth.com/videos/prealgebra/pre-algebra-videos.php

Tagged under: formula,area circle,pi squared,pi square,proof,7th grade,math,pre-algebra,area,circle

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