Common Core 2025 Circle Math: Find Circumference & Area in Terms of π (Radius 3) | Explanation
Learn how to use the circle formulas to express circumference and area in terms of π when the radius is given. Perfect practice for Grade 5 placement tests and foundational geometry.
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What you'll learn
- Identify radius and plug it into the correct formula
- Compute circumference as a multiple of π without decimals
- Compute area using r² and keep answers in terms of π
- Fill in coefficient blanks quickly and accurately
About this lesson
Given a circle with radius 3, how do you write the circumference in terms of π? How do you find the area in terms of π without turning π into a decimal? In this quick walkthrough, you’ll apply C = 2πr and A = πr² step by step. By the end, you’ll confidently fill in the missing coefficients for 6π and 9π.
If the radius is 3, use the standard circle formulas and keep π as a symbol. You’ll end up with a circumference of 6π and an area of 9π.
How do you find circumference and area in terms of π?
Circumference: Use C = 2πr. Substitute r = 3: C = 2π(3) = 6π, so the blank is 6.
Area: Use A = πr². Substitute r = 3: A = π(3²) = π(9) = 9π, so the blank is 9.
Tip: When a problem says “in terms of π,” don’t approximate π—just simplify the number in front of π.
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