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Bourke High School - Area of an Annulus

This applet calculates the area of an annulus, having a larger radius R and a smaller radius r. The two radii can be varied by moving the black dots where the labels 'Outer' and 'Inner' are shown. Use the applet to answer the following questions: 1. What is the formula for the area of an annulus? 2. By varying the radii, what is the smallest and largest area of the applet's annulus?