O is the center of the circle in the figure below.
What is its circumference?
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O is the center of the circle in the figure below.
What is its circumference?
We use the formula:
We replace the data in the formula:
cm
O is the center of the circle in the diagram.
What is its perimeter?
The circumference formula C = 2πr comes from the fact that circumference = π × diameter. Since diameter = 2 × radius, we get C = π × (2r) = 2πr.
Keep it as 16π unless specifically asked for a decimal! The exact form with π is more precise than rounding to 50.27.
Circumference measures the distance around the circle (like a fence), while area measures the space inside the circle (like grass in a yard).
Think of circumference as the 'rim' of the circle. Since it's a distance, use C = 2πr. Area fills the inside, so it needs r² (A = πr²).
You can use π ≈ 3.14159, but it's usually better to leave answers in exact form with π unless told otherwise. Many problems expect the π to remain.
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