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

Exercise 3 Page 480

Use the formula for finding the circumference of a circle.

6048.6yd^2

Practice makes perfect
We want to find the area of a circle with circumference of 25.12 meters. Remember that the area of a circle with radius r is calculated using the formula below. A=π r^2 Here, r is the radius of the circle. To find the area, we need to start by finding the value of the radius of the circle. Since the circumference is 88yd, we can use the formula for the circumference to find the radius of the circle. C=2π r We will substitute 88 for C in the formula and solve the resulting equation for r. We will use 227 for π.
C=2 π r
88=2( 22/7) r
88=(2 * 22/7) r
88=(44/7) r
7* 88 = 7 * (44/7) r
7* 88 = 44 * r
616=44r
616/44=44r/44
14=r
We found that the radius of the circle is 44 yards. Now, we can substitute r= 44 into the formula for the area of a circle. Do not forget to use 227 for π.
A=π r^2
A= 22/7 * 44^2
A=22/7 * 1936
A=22 * 1936/7
A=42 592/7
A=6084.571428 ...
A≈ 6048.6
The area of the circle is 6048.6yd^2.

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.