Circumference is the distance around a circle (perimeter).
A great way to remember this formula is by singing the "Twinkle Twinkle Little Star" song:

"Twinkle twinkle little star,
Circumference equals two pi r."

Formulas: πd or 2πr

remember: the radius is half the diameter, which is why EITHER of these formulas will work! Pretty groovy?
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Area is the space covered inside the shape, in this case, the circle.
We can use this rhyme to help us remember the formula:

"Fuzzy Wuzzy was a bear,
Area equals pi r squared."

Formula: πr^2

*Be careful. You must be able to correctly identify the diameter and radius and substitute the values into your formulas.

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