# How Do You Find The Diameter Of A Circle?

The diameter is defined as a straight line which passes through the centre of a circle. It connects two points on the circumference of the circle. It is a straight line that connects the centre of the circle with two points on the perimeter of the circle. It also connects the centre of the sphere with two points on its surface.

The diameter of a circle is twice the radius of the circle. In other words, the radius of a circle is half the diameter of the circle. The word diameter is derived from two Greek words diairo, which means divide and metro, which means measure. It is a straight line segment. It passes through the centre of the circle. In other words, it is the line which divides a full circle into two semi-circles. A diameter is a chord. It is a chord that passes through the midpoint or centre of a circle.
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You would divide the circumference by pi or 3.14
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Diameter equals radius times 2 so 3 times 2
radius is half of the diameter
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If you are just given a circle, nothing else, here is what you can do -

find a piece of paper with right angle (index card, print paper, envelope...), follow the steps to estimate the diameter of your circle:

1)  place the tip of the right angle (paper) on the circle, mark it to be A

2) draw a chord on the given circle along the edge of the paper (if paper is too small for your circle, extend it with a ruler). Mark it to be chord AB

3) draw a second chord on the circle along the perpendicular side of the paper. Mark it to be AC.

4) connect BC and this should be your diameter. Find mid point of it and this should be your radius.

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The diameter of the circle is the longest chord of it. A chord is a straight line joining any two points of a circle.Diameter is twice the radius in length and it also passes through the centre of the circle.It also divides the circle into two equal halves each forming a semicircle.
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The Diameter of a circle is the distance across a circle through its center point. If you know the radius of the circle, the diameter can be found by using a simple formula which is as follows:
Diameter= 2R where R stands for the radius of the circle.
In the above case, the diameter will be 2(3)= 6cm. Is your required answer
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Circumference is 13 3/4 inches
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How do I find the diameter of a circle when all I know is the circumference
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The longest possible straight line passing through the center and contained within the circumference of a circle
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The diameter is twice the radius.
D= 2 times  r
d= 2 (3) cm
d= 6 cm
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The distance across the circle, through its center, is the diameter of the circle. The diameter is twice the radius.

Don't blame me, I got it from my current Geometry book. I hope this helps!
-Esther Etsuka Wu
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The diameter of a circle is the widest line that passes across the width of a circle. It also necessarily has to pass through the centre of the circle. Every line that runs from the central point of the circle to its circumference is the radius of the circle and is half the length of the circle. Hence the formula of diameter is D=2R; where D is diameter and R is the radius. Another method to calculate a circles diameter is if the area or the circumference of the circle are known. The formula for area of a circle is r2 or that for circumference is d. The formulas can be reversed where radius will be the root of area divided by , or using the second formula where diameter will be circumference divided by .
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By smelling it.
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Assuming you want to find the measure of the diameter, you can ...

2. Draw a line through the center and measure the length of the line.
3. Turn it every which way in the sunlight and measure the greatest width (not length) of the shadow.
4. Measure the distance from a (tangent at two places) right angle corner to the circle and perform a calculation.

Assuming you want to construct a line that is a diameter of the circle, you can draw a chord and construct the perpendicular bisector. The diameter is the measure of that bisector between the points where it intersects the circle.
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