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By a 21-inch circle I presume you mean that the diameter is 21 inches. So the radius is half as long, 10.5 inches. The formula for the circumference of a circle is 2 pi r, where r is the radius. Pi is about 3.14. That is accurate to 2 decimals, or 3 significant digits all together. I use that approximation because the dimension we are given has 2 significant digits. So the circumference is pi times the diameter; we multiply 3.14 by 21 inches and get 65.94. To 2 significant digits, that is 66 inches. If you meant that the radius was 21 inches, then the circumference would be twice as much, or 132 inches.
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How do solve circumference?
The circumference of a circle is 2*pi*radius or diameter*pi
How do you get the radius of a circle from the circumfrance?
To find the radius of a circle when given the circumference, you should start with the formula for circumference, which is this: circumference = 2*pi*radius To solve for the radius, you would the have to divide the circumference by 2*pi leaving you with a formula like this: radius = circumference/(2*pi) pi≈3.14159
If a circumference of a circle is 28.26 inches what is the radius of the circle?
Well, isn't that a happy little question! To find the radius of a circle when you know the circumference, you can use the formula: circumference = 2πr. So, if the circumference is 28.26 inches, you can plug that in and solve for the radius. Just divide the circumference by 2π (which is about 6.28) to find the radius. Happy calculating!
What name is given to the perimeter of circle?
The perimeter of a circle is its circumference
What is the circumference a circle?
The round perimeter of circle is its circumference
