What is Radius?
The distance from the center of a circle to any point on the circle itself is exactly the same. This distance is called the radius of the circle.
What is Diameter?
The diameter is the length of the line through the center that touches two points on the edge of the circle.
TOP DIFFERENCES BETWEEN RADIUS AND DIAMETER:
| The radius is the length from the midpoint of the circle to the outer edge of the circle. | Diameter is the full length of the circle running from the edge, through the midpoint, all the way to the other side. |
| The radius is represented by the lowercase letter “r.” | The diameter of a circle is represented by the letter “d.” |
| The radius of a circle runs from its center to its edge. | diameter runs from edge to edge and cuts through the center. |
| radius (r=d2)! | diameter (d=2r) |
Conclusion:
The Radius is the distance from the center outwards. The Diameter goes straight across the circle, through the center. The Circumference is the distance once around the circle. Both Radius and Diameter are related to a circle only.
Also, Read Differences between Symmetrical and Asymmetrical.
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After you've chosen a point to be the center of a circle and know how far that point is from all the points that lie on the circle, you can draw a fairly decent picture.\r\n\r\nWith the measure of the radius, you can tell a lot about the circle: its <em>diameter</em> (the distance from one side to the other, passing through the center), its <em>circumference</em> (how far around it is), and its <em>area</em> (how many square inches, feet, yards, meters — what have you — fit into it).\r\n\r\n<img src=\"//sg.cdnki.com/what-are-radius-and-diameter---aHR0cHM6Ly93d3cuZHVtbWllcy5jb20vd3AtY29udGVudC91cGxvYWRzLzQzOTYyMS5pbWFnZTAuanBn.webp\" alt=\"image0.jpg\" width=\"535\" height=\"168\" />\r\n\r\nAncient mathematicians figured out that the circumference of a circle is always a little more than three times the diameter of a circle. Since then, they narrowed that “little more than three times” to a value called <em>pi</em> (pronounced “pie”), designated by the Greek letter <em>π</em>.\r\n\r\nThe decimal value of <em>π</em> isn't exact — it goes on forever and ever, but most of the time, people refer to it as being approximately 3.14 or 22/7, whichever form works best in specific computations.\r\n\r\nThe formula for figuring out the circumference of a circle is tied to <em>π</em> and the diameter:\r\n<blockquote>Circumference of a circle: <em>C</em> = <em>πd</em> = 2<em>πr</em></blockquote>\r\nThe <em>d</em> represents the measure of the diameter, and <em>r</em> represents the measure of the radius. The diameter is always twice the radius, so either form of the equation works.\r\n\r\nSimilarly, the formula for the area of a circle is tied to <em>π</em> and the radius:\r\n<blockquote>Area of a circle: <em>A</em> = <em>πr</em><sup>2</sup></blockquote>\r\nThis formula reads, “Area equals pi are squared.”\r\n\r\nFind the radius, circumference, and area of a circle if its diameter is equal to 10 feet in length.\r\n\r\nIf the diameter (<em>d</em>) is equal to 10, you write this value as <em>d</em> = 10<em>.</em> The radius is half the diameter, so the radius is 5 feet, or <em>r</em> = 5<em>.</em> You can find the circumference by using the formula\r\n\r\n<img src=\"//sg.cdnki.com/what-are-radius-and-diameter---aHR0cHM6Ly93d3cuZHVtbWllcy5jb20vd3AtY29udGVudC91cGxvYWRzLzQzOTYyMi5pbWFnZTEucG5n.webp\" alt=\"image1.png\" width=\"246\" height=\"20\" />\r\n\r\nSo, the circumference is about 31.5 feet around. You find the area by using the formula\r\n\r\n<img src=\"//sg.cdnki.com/what-are-radius-and-diameter---aHR0cHM6Ly93d3cuZHVtbWllcy5jb20vd3AtY29udGVudC91cGxvYWRzLzQzOTYyMy5pbWFnZTIucG5n.webp\" alt=\"image2.png\" width=\"312\" height=\"24\" />\r\n\r\nso the area is about 78.5 square feet.","description":"A <em>circle</em> is a geometric figure that needs only two parts to identify it and classify it: its <em>center</em> (or middle) and its <em>radius</em> (the distance from the center to any point on the circle). 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With the measure of the radius, you can tell a lot about the circle: its diameter (the distance from one side to the other, passing through the center), its circumference (how far around it is), and its area (how many square inches, feet, yards, meters — what have you — fit into it).
Ancient mathematicians figured out that the circumference of a circle is always a little more than three times the diameter of a circle. Since then, they narrowed that “little more than three times” to a value called pi (pronounced “pie”), designated by the Greek letter π.
The decimal value of π isn't exact — it goes on forever and ever, but most of the time, people refer to it as being approximately 3.14 or 22/7, whichever form works best in specific computations.
The formula for figuring out the circumference of a circle is tied to π and the diameter:
Circumference of a circle: C = πd = 2πrThe d represents the measure of the diameter, and r represents the measure of the radius. The diameter is always twice the radius, so either form of the equation works.
Similarly, the formula for the area of a circle is tied to π and the radius:
Area of a circle: A = πr2This formula reads, “Area equals pi are squared.”
Find the radius, circumference, and area of a circle if its diameter is equal to 10 feet in length.
If the diameter (d) is equal to 10, you write this value as d = 10. The radius is half the diameter, so the radius is 5 feet, or r = 5. You can find the circumference by using the formula
So, the circumference is about 31.5 feet around. You find the area by using the formula
so the area is about 78.5 square feet.