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
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.
To find the circumference of a circle when you know the area, you first need to find the radius of the circle using the formula for the area (area = πr^2). Once you have the radius, you can calculate the circumference using the formula for the circumference (circumference = 2πr).
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.
Area of a circle = pi*radius2