Common Core: 7th Grade Math : Know and Use the Formulas for the Area and Circumference of a Circle: CCSS.Math.Content.7.G.B.4

Study concepts, example questions & explanations for Common Core: 7th Grade Math

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Example Questions

Example Question #1 : How To Find Circumference

Ashley has a square room in her apartment that measures 81 square feet. What is the circumference of the largest circular area rug that she can fit in the space?

Possible Answers:

\(\displaystyle 81\pi\)

\(\displaystyle 8\pi\)

\(\displaystyle 18\pi\)

\(\displaystyle 9\pi\)

\(\displaystyle 10\pi\)

Correct answer:

\(\displaystyle 9\pi\)

Explanation:

In order to solve this question, first calculate the length of each side of the room. 

\(\displaystyle A=s^2\)

\(\displaystyle 81=s^2\)

\(\displaystyle s=9\)

The length of each side of the room is also equal to the length of the diameter of the largest circular rug that can fit in the room. Since \(\displaystyle C=\pi d\), the circumference is simply

\(\displaystyle C=9\pi\)

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