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Since the formula for the area of a circle is pi times the radius squared and the formula for the circumference is two times pi times the radius, you would find the circumference by first dividing by pi. This would give you the radius squared. Find the square root of this value. This will give you the length of the radius. Take this length and multiply it by two times pi.

Q: How do you find the circumfrence of a circle if you only know the area?

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We know that 2πr=circumference (or πxdiameter) So simply re-arrange the equation to get r=circumference/2π Now that you have r, πr^2=area

Pi x the diameter of the circle will hive you the circumference. The diameter is double the radius so the answer to your question is pi2r.

Do you know how to find the area of a circle when you know the radius ? Good! Do that. Do you know how to find the area of a square when you know the length of the side ? Good! Do that. Now you have two numbers ... the area of the circle and the area of the square. The problem wants you to find the difference of these two numbers. Do you know how to use subtraction to find the difference of two numbers ? Good! Do that.

A semicircle is 1/2 of a circle. Find the area with the diameter you are given as if you had a whole circle, then divide that answer by 2 to get the area of the semicircle.

Area of a circle equals pi r2 Therefore the radius of a circle equals the square root of (area divided by pi).

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If you do not have the area, what do you have? The radius is half the diamiter The radius is PieR2 Worked backwards if you know the circumfrence.

radius = circumference/(2*pi)

If you know the diameter of the circle, multiply that by Pi (about 3.1416). The result is the circumference.

We know that 2πr=circumference (or πxdiameter) So simply re-arrange the equation to get r=circumference/2π Now that you have r, πr^2=area

Pi x the diameter of the circle will hive you the circumference. The diameter is double the radius so the answer to your question is pi2r.

Circumfrence is the perimeter of a circle, the line that makes a circle looks like a circle Imagine a perfect circle drawn on a piece of paper. Take the length of the line of the circle (by line I mean the part that is actually drawn on the piece of paper the ring) and there, you have the circumfrence. The circumfrence is exactly π times the size of the diameter (if you don't know what those two things are ignore this)

Area of a circle = pi*radius2

Do you know how to find the area of a circle when you know the radius ? Good! Do that. Do you know how to find the area of a square when you know the length of the side ? Good! Do that. Now you have two numbers ... the area of the circle and the area of the square. The problem wants you to find the difference of these two numbers. Do you know how to use subtraction to find the difference of two numbers ? Good! Do that.

Wow, a question I actually know! The radius of a circle is 1/2 of the circumfrence. In other words, if your body was a circle, and you spread out youre arms, the area from you're heart to the tip of you're fingers would be the radius.

The circumference (c) of a circle = 2πr (where r = radius). Therefore if you know the circumference, the radius (r) = c/2π.

A semicircle is 1/2 of a circle. Find the area with the diameter you are given as if you had a whole circle, then divide that answer by 2 to get the area of the semicircle.

In order to find the diameter of a circle if you have the area is to rearrange the formula for the area of a circle to put diameter as the unknown, like so: PIE*d = Area of a Circle d = (Area of a Circle) / PIE Therefore if the area of your circle is 40cm, 40/PIE = 12.73cm and that's the diameter.