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Coordinate Geometry Videos 28 videos
ACT Math: Coordinate Geometry Drill 1, Problem 1. Which inequality is expressed by the number line?
ACT Math: Coordinate Geometry Drill 3, Problem 3. What is the standard form equation for the line?
ACT Math: Coordinate Geometry Drill 2, Problem 4. What is the equation for the circle in the video?
ACT Math 5.1 Plane Geometry 327 Views
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Description:
ACT Math: Plane Geometry Drill 5, Problem 1. What is the area of the circle?
Transcript
- 00:02
Time for your daily dose of Shmoop. This won't hurt a bit.
- 00:06
A circle has a circumference of 12π. What is the area of the circle?
- 00:10
And here are your options...
- 00:15
Okay, so we're given the circumference and we're looking for the area.
- 00:19
Hopefully, we remember the formula for the circumference of a circle: Diameter times pi
Full Transcript
- 00:19
Hopefully, we remember the formula for the circumference of a circle: Diameter times
- 00:24
We're told that a circle has a circumference
- 00:26
of 12 pi...which means the diameter of this circle is 12.
- 00:31
If the diameter is 12, the radius is exactly half of that... 6.
- 00:36
The area of a circle is equal to π times radius squared,
- 00:39
and now that we have the radius, we just have to plug in that value.
- 00:44
6 squared is 36...so we get 36π as our answer, which is choice C.
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