2007-05-29 15:07:05 · 9 answers · asked by apollo1950 1 in Science & Mathematics ➔ Mathematics
Um...
Not to seem rude and answer with a question, but...
In relation to what?
If we're not talking relative size here, then you just take a measurement. But I'm sure you're not looking for instructions on how to use string and a ruler.
The rule is that a circle's circumference is equal to twice the radius times Pi. Twice the radius is the diameter. Pi is 3.14... (and we need not be more specific for home use)
Circumference = 2 Pi r
The other rule is that the area of a circle is equal to the Pi times the radius squared. Squared is "to the second power".
Area = Pi r^2
It may seem odd that both have Pi, radius, and a "2" in the equation, but remember that "area" produces "square feet". Well, "square" something, so that uses the equation with the "power" or exponent in it.
As a side note, these things only hold true with Cartesian geometry and algebra. "Cartesian" denotes a flat, two-dimensional space. We don't actually live in a flat, two-dimensional space. Even the circle we draw on paper isn't really a flat, two-dimensional thing - although it is a flat, two-dimensional picture. However, fear not of the 11 dimensional nature of the universe and what a circle really is, and just remember...the rules work just fine for home use.
2007-05-29 15:22:03 · answer #1 · answered by Anonymous · 0⤊ 0⤋
Diameter times pi.
Or 2 times radius times pi.
2007-05-29 22:10:41 · answer #2 · answered by Wise_Guy_57 4 · 0⤊ 0⤋
Pi times 2r (where r= the radius, and Pi is apx 3.14, in most cases though you leave it in the Pi form, unless you are estimating)
OR
Pi times D (where d=diameter, the diameter is 2 times the radius if you don't have the diameter, hence why you have above equation Pi times 2r)
I hope this helps.
2007-05-29 22:24:32 · answer #3 · answered by Soci chick 1 · 0⤊ 0⤋
diameter times pi. area is pi times the radius squared
2007-05-29 22:10:55 · answer #4 · answered by ash ear edlamb amatch and astick 2 · 0⤊ 0⤋
Pi(D)-Pi times Diameter
Pi(2r)-Pi times 2 times the radious.
2007-05-29 22:13:02 · answer #5 · answered by Chiva$ 4 Life 3 · 0⤊ 0⤋
Radius times pi. Pi is 3.14.
2007-05-29 22:11:59 · answer #6 · answered by RANGE ROVERS ROCK!!!!!! 2 · 0⤊ 0⤋
radius times pi? that or diameter times pi
2007-05-29 22:10:00 · answer #7 · answered by eric f 2 · 0⤊ 0⤋
you multiply 2 by the radius and then multiply that by pi, or you can multiply the diameter by pi, (it's the same thing)
2007-05-29 22:11:32 · answer #8 · answered by Darren 2 · 0⤊ 0⤋
C = Ï d or = 2 Ï r
(where d is diameter and r is radius)
2007-05-30 03:16:59 · answer #9 · answered by Como 7 · 0⤊ 0⤋