7.4 Measuring Circles

Beginning Lesson

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As the World Turns (MS)

How fast is the Earth spinning? Students use unit rates to find the speed at which the planet rotates along the Equator, Tropic of Cancer, and Arctic Circle.

Topic: Expressions and Equations (EE), Ratios and Proportional Relationships (RP)

Middle Lessons


F-Stop in the Name of Love

How do camera settings affect the final image, and how can we use aperture and shutter speed to take better pictures? Students use the area of circles and fractions to explore how to properly expose a picture, and how photographers use depth of field and motion blur to get the perfect shot.

Topic: Geometry (G)
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Spinning Your Wheels

Why do tires appear to spin backwards in some car commercials? Students apply unit rates and the formula for the circumference of a circle to determine what makes a spinning wheel sometimes look like it’s moving in the opposite direction of the car sitting on top of it.

Topic: Geometry (G), Ratios and Proportional Relationships (RP)

End Lesson


Pizza Pi

Should you ever order a personal-sized pizza from Pizza Hut? Students calculate circle areas to compare the unit costs of different sized pizzas, find the percent of pizza that is tasty inside vs. crust, and debate whether it’s ever a good idea to order a personal-sized pizza from Pizza Hut.

Topic: Geometry (G)