Envision Math 2.0: Grade 7, Volume 2
EM
Envision Math 2.0: Grade 7, Volume 2 View details
5. Solve Problems Involving Circumference of a Circle
Continue to next subchapter

Exercise 11 Page 445

Use the formula for finding the circumference of a circle.

8.6cm

Practice makes perfect
We want to find the diameter of a circle with a circumference of 27 centimeters. Remember that the circumference of a circle with radius r is calculated using the formula below. C=2π r We will substitute 27 for C in the formula and solve the resulting equation for r. We will use 3.14 for π.
C=2 π r
27=2π r
27/2π=2π r/2π
27/2π=2π r/2π
27/2π=r
4.299363...=r
4.3 ≈ r
We found that the radius of the circle is approximately 4.3 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 * 4.3 = 8.6 The diameter is 8.6 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.