Envision Math 2.0: Grade 7, Volume 2
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Envision Math 2.0: Grade 7, Volume 2 View details
Review

Exercise 2 Page 480

Use the formula for finding the circumference of a circle.

40.2cm

Practice makes perfect
We want to find the diameter of a bicycle tire with a circumference of 126.5 centimeters. Remember that the circumference of a circle with radius r is calculated using the formula below. C=2π r We will substitute 126.5 for C in the formula and solve the resulting equation for r. We will use 3.14 for π.
C=2 π r
126.5=2π r
126.5/2π=2π r/2π
126.5/2π=2π r/2π
126.5/2π=r
20.143312...=r
20.1 ≈ r
We found that the radius of the circle is approximately 20.1 centimeters. Since the diameter is twice the length of the radius, we can multiply the radius by 2 to find the diameter of the circle. d= 2 * 20.1 = 40.2 The diameter is 40.2 centimeter.

Extra

More About Circles!

Are you interested in learning more about circles? Our Mathleaks original content can teach you all about them! Check out the following resources to see real-world uses for circumference and area, how circles compare to other shapes and why, as well as some higher level topics that you can look forward to learning about in Geometry and Algebra 2.