Grade level: 5 – 6th grades

Skills: Radius, diameter, circumference & area of a circle

Related environmental issues: Energy

The size of wind turbine has been getting larger to generate electricity from wind more efficiently.  About 75% of the wind turbines built in 2014 in the United States had a rotor diameter of 100 meters. “100 meters” is about the same as the length of a Football Pitch.

1. What is the radius?

2. What is the circumference?

3. What is the area?

Source: American Wind Energy Association,  Market Report

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Answer keys

1.  50 meters (100/2 = 50)

2.100π m(2 x π x 50 = 100π)

3.  2,500π m2 (π x 50 x 50 = 2,500π)