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How does the radius, diameter, and circumfrence of a cicle work?

+11 votes
8,317 views
asked Mar 8, 2013 in Math by Dante101 (720 points)


4 Answers

+1 vote
answered Jun 19, 2013 by smile828 (32,100 points)
The diameter is a line that cuts through the center of the circle. The radius is a line that comes from the diameter to the edge of the circle. The crcumference is pie * diameter. The area is the radius squared( the number times itself) times pie.

Hope this helps!!!
+1 vote
answered Mar 28, 2013 by Cupcake549 (32,490 points)
I am not the best at math so I do not know I learned them last year but I dont like math so it did not stick in my head.
+1 vote
answered Mar 17, 2013 by mystic_beauty (17,920 points)
They are connected. The diameter is the measure across the circle's face. Radius is half of that. Circumfrence is the measure AROUND a circle. See? They're connected! The number Pi also relates. You multiply the diameter by 3.14 (pi) to get the circumfrence.

-CraftyGirlJuJu
+2 votes
answered Mar 9, 2013 by whizkid (65,660 points)
edited Dec 20, 2014 by whizkid
They are all connected. Diameter is just how wide it is by drawling a straight line that passes through the center from one side to the opposite end. It does not matter where you start the line because the diameter does not change. It will always be the biggest width possible.

Radius is half the Diameter. Example: Diameter is 10 feet, so Radius is just 10/2 = 5 feet. It is the distance from the center of a circle to the outside of it.

Circumference is a measure of the outside circle length. Imagine you are taking a walk around the circle on the edge. When you get back to your starting point that is the circumference.

Now, there is a special number called pi that links these things all together. pi is the ratio of the circumference / diameter. That number is always constant and about 3.14 (actual number goes on forever, but that is more complicated and 3.14 is good enough most of the time).

If you only know the radius, I can get the diameter by doubling it.

Radius = 5, Diameter = 10

Since pi = Circumference / Diameter, I can calculate the Circumference just by taking the Diameter times pi. Example: Diameter = 10 ft, so Circumference is 10 ft X 3.14 = 31.4 ft.  Area is pi X radius squared, but that is more advanced.
commented Dec 13, 2014 by anonymous

10 ft X 3.14 = 13.4 ft. huh?  

commented Dec 20, 2014 by whizkid (65,660 points)
Oops. I fixed it. Thanks for catching it.

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