How to Measure Circumference of a Circle

Searching for circumference of a circle formula ? let me explain you how to find the circumference of a circle,

* Measure diameter. The diameter of a circle is the distance across a circle, through its center. It can be visualized as a straight line cutting the circle in half. For large circles like running paths, the diameter can be estimated.

* Consider radius. Radius is the distance from the center of a circle to any point on the circle. The radius of a circle is half its diameter. When diameter is too large to determine, estimate the radius. Then use simple math and multiply the radius by 2.

* Grasp pi. Pi is the ratio of the circumference of a circle to its diameter. Pi is called a constant in math. It is a number that does not change, no matter the size of the circle. The value of pi is usually rounded to 3.14.* Calculate circumference. Use simple math to multiply the diameter of the circle by pi. If a jogger estimated diameter of a circular path as 200 meters across, then circumference would be 200 times 3.14 or 628 meters.

* Verify units of measurement. The units for circumference are the same as the units for diameter. If diameter is measured in meters, report circumference in meters.

I hope the above explanation was useful.

Explain Concentric circles

Let us study about concentric circles,
In a large circle, two or more small circles inside a large circle and the center for all the circle inside is same. Other wise circle which have common center are known as concentric circle.

Wher R is the radius of the large circle, and r is the radius of the small circle.

In the figure we see that the center is same for both the circle.

For concentric circle we can find the area of ring inside large circle and small circle is given by.

Area of a ring = Area of large circle - area of small circle

= πR2 - πr2

= π(R+r)(R-r) Square units

Let us example for area of a ring in a concentric circle.

I hope the above explanation was useful, now let me explain how to find area of circle.

Perimeters and Areas of similar triangles

Let us learn about perimeters and areas of similar triangles,
When two triangles are similar, the reduced ratio of any two corresponding sides is called the scale factor of the similar triangles. In Figure 1 , Δ ABC∼ Δ DEF.

Figure 1 Similar triangles whose scale factor is 2 : 1.

The ratios of corresponding sides are 6/3, 8/4, 10/5. These all reduce to 2/1. It is then said that the scale factor of these two similar triangles is 2 : 1.
The perimeter of Δ ABC is 24 inches, and the perimeter of Δ DEF is 12 inches. When you compare the ratios of the perimeters of these similar triangles, you also get 2 : 1. This leads to the following theorem.
Theorem : If two similar triangles have a scale factor of a : b, then the ratio of their perimeters is a : b.
Hope the above explanation helped you.