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Teachers & SchoolsACT Math: Plane Geometry Drill 5, Problem 1. What is the area of the circle?

ACT Math | Plane Geometry |

ACT Mathematics | Plane Geometry |

Circles | Equations of Circles |

Coordinate Geometry | Conics |

Foreign Language | Arabic Subtitled Chinese Subtitled Korean Subtitled Spanish Subtitled |

Language | English Language |

Plane Geometry | Area |

Product Type | ACT Math |

Hopefully, we remember the formula for the circumference of a circle: Diameter times

We're told that a circle has a circumference

of 12 pi...which means the diameter of this circle is 12.

If the diameter is 12, the radius is exactly half of that... 6.

The area of a circle is equal to π times radius squared,

and now that we have the radius, we just have to plug in that value.

6 squared is 36...so we get 36π as our answer, which is choice C.