To calculate the radius of a circle by using the circumference, take the circumference of the circle and divide it by 2 times π. For a circle with a circumference of 15, you would divide 15 by 2 times 3.14 and round the decimal point to your answer of approximately 2.39
You already know the radius.
circumference of a circle = diameter*pi or 2*pi*radius
OK, SO to find the area of a circle, you find the radius (half of the diameter), and fit it into the equation πr2=A where r equals radius and A = area. The perimeter of a circle is π multiplied by the diameter. π is ≈ 3.1415296.
It depends on the values you have. The base of a cylinder is a circle. If you know the circle's diameter, half it to find the radius. If you know the circle's circumference, divide by 2pi to find the radius. If you know the circle's area, divide by pi and take the square root to find the radius.
Diameter = 2*Radius
measure it
It's important to know the formulas for all these characteristics of circles, and to recognize what they have in common. Area of a circle = πr2 Circumference of a circle = 2πr or dπ Where in the above equations r represents radius, and d is diameter (2r). Both these equations have r in them. Find the radius using the circumference equation, and then plug it into the equation for Area
radius = circumference/(2*pi)
radius = circumference/2*pi
Area of Circle = pi (radius)2 So , using this formula we can find the radius and also the diameter. Diameter = 2(radius)
You can measure it. Otherwise, you certainly have to know SOMETHING about the circle to calculate the radius, usually the diameter, the circumference, or the area. If you don't know anything at all about a circle, you can't find out the radius, either.
To find the radius you should either know the area or the circumference. The area is found by multiplying the radius squared by pi which is 3.14159 The equation is ... A=pi x r2 The area is the total amount of space inside the circle The circumference is found by multiplying 2 and pi and radius together. The equation is ... C=2 x pi x r The circumference is the total amount of length around the outside of the circle. So with this information you should be able to find the length of the radius. If your not sure what the radius is. The radius is the length from the center of the circle to one of the points on the outer side of the circle. The radius is the same distance to any point on the outer side of the circle as long as the radius starts in the middle point of the circle.