Area List » circle area http://www.thearealist.com Fri, 03 Feb 2012 07:36:48 +0000 http://wordpress.org/?v=2.8.4 en hourly 1 How do you find the diameter of a circle given the area? Explain and then answer the following question!? http://www.thearealist.com/circle-area/how-do-you-find-the-diameter-of-a-circle-given-the-area-explain-and-then-answer-the-following-question http://www.thearealist.com/circle-area/how-do-you-find-the-diameter-of-a-circle-given-the-area-explain-and-then-answer-the-following-question#comments Thu, 13 Jan 2011 21:54:19 +0000 admin http://www.thearealist.com/circle-area/how-do-you-find-the-diameter-of-a-circle-given-the-area-explain-and-then-answer-the-following-question Find the diameter of a certain circle with an area of 56.5 square inches?

use algabra with the formula pi*r^2=area

so divide by pi, then take the square root of that.

]]> http://www.thearealist.com/circle-area/how-do-you-find-the-diameter-of-a-circle-given-the-area-explain-and-then-answer-the-following-question/feed 11 How do solve for the area of an inscribed circle or a polygon? http://www.thearealist.com/circle-area/how-do-solve-for-the-area-of-an-inscribed-circle-or-a-polygon http://www.thearealist.com/circle-area/how-do-solve-for-the-area-of-an-inscribed-circle-or-a-polygon#comments Mon, 20 Dec 2010 21:34:01 +0000 admin http://www.thearealist.com/circle-area/how-do-solve-for-the-area-of-an-inscribed-circle-or-a-polygon I need to know. Given the measurement or area of a polygon or circle, how do you find out the area of another circle or polygon sincribed in it?

Let
A=Area of the inscribed circle
B=Area of the Polygon
r=radius of circle
a=a side of the Polygon

A=π*r^2
B=5*a*r/2

we need only the relationship between r and a :
first see that we can find a triangle that r is its height, a/2 is its hypotenuse and r is perpendicular to a/2. Besides the angle next to r and in front of a/2 is 360/10 =36 degree.
So:
a/2=r*tangent (36)

Now Let a in B=5*a*r/2
B=5*tangent (36)*r^2

Divide A to B:
A/B = π/(5*tangent (36))

And you can get:
A=B*π/(5*tangent (36))

So, given area of the Polygon B, you can find the Area of the inscribed circle A

]]> http://www.thearealist.com/circle-area/how-do-solve-for-the-area-of-an-inscribed-circle-or-a-polygon/feed 3 Finding radius of a circle by its area? http://www.thearealist.com/circle-area/finding-radius-of-a-circle-by-its-area http://www.thearealist.com/circle-area/finding-radius-of-a-circle-by-its-area#comments Sat, 18 Dec 2010 20:32:58 +0000 admin http://www.thearealist.com/circle-area/finding-radius-of-a-circle-by-its-area Suppose there was a circle, the area of which is 400,000 units. What would the radius of that circle be?

The formula for the area of a circle is pi times r2. To find the radius, divide the area by pi then find the square root of that answer.

400000/3.14 = 127388.5350318471
√127388.5350318471 = 356.9153051241248
Hope that helped! :D

]]> http://www.thearealist.com/circle-area/finding-radius-of-a-circle-by-its-area/feed 1 Finding the radius of a circle using the area of a sector and its angle? http://www.thearealist.com/circle-area/finding-the-radius-of-a-circle-using-the-area-of-a-sector-and-its-angle http://www.thearealist.com/circle-area/finding-the-radius-of-a-circle-using-the-area-of-a-sector-and-its-angle#comments Tue, 14 Dec 2010 20:45:12 +0000 admin http://www.thearealist.com/circle-area/finding-the-radius-of-a-circle-using-the-area-of-a-sector-and-its-angle The area of the sector is 16m^2 and the central angle is 2 rad. Find the radius of the circle?

Area of a circle / angle at the centre = Area of a sector / angle subtended at the centre.

πr² / 2π = 16 / 2
r² / 2 = 8
r² = 16 therefore r = √16 = 4 (positive root only is required)

]]> http://www.thearealist.com/circle-area/finding-the-radius-of-a-circle-using-the-area-of-a-sector-and-its-angle/feed 1 What is the relationship between the diameter of a circle and the area of the circle? http://www.thearealist.com/circle-area/what-is-the-relationship-between-the-diameter-of-a-circle-and-the-area-of-the-circle http://www.thearealist.com/circle-area/what-is-the-relationship-between-the-diameter-of-a-circle-and-the-area-of-the-circle#comments Sun, 12 Dec 2010 17:28:55 +0000 admin http://www.thearealist.com/circle-area/what-is-the-relationship-between-the-diameter-of-a-circle-and-the-area-of-the-circle What is the relationship between the diameter of a circle and the area of the circle?

Let diameter = d
radius = r
We know that radius is half of diameter.
That is r = d/2.

Equation for area of a circle A = πr²
=π(d/2)²
= πd²/4

]]> http://www.thearealist.com/circle-area/what-is-the-relationship-between-the-diameter-of-a-circle-and-the-area-of-the-circle/feed 4 How to find the area only given the circumference of a circle? http://www.thearealist.com/circle-area/how-to-find-the-area-only-given-the-circumference-of-a-circle http://www.thearealist.com/circle-area/how-to-find-the-area-only-given-the-circumference-of-a-circle#comments Fri, 10 Dec 2010 20:08:48 +0000 admin http://www.thearealist.com/circle-area/how-to-find-the-area-only-given-the-circumference-of-a-circle A=πr^2 is area of circle. But only given the circumference (C) such as 16π mm. And given the diameter (d) the circumference can be found by C=πd or d=2r (radius), so C=2πr, Okay so basically asking how to find the area of a circle, given the circumference, and using the circumference to find the diameter, and using the diameter to find the radius. I can’t work backwards yet…my book doesn’t give me the formula for that.

c = 2 pi*r => r = c/2pi
=> area = pi(c/2pi)^2
Here c = 2pi r = 16 pi => r = 8 mm
=> Area = 64 pi sqmm.

]]> http://www.thearealist.com/circle-area/how-to-find-the-area-only-given-the-circumference-of-a-circle/feed 8 How do you find the circumference of a circle when you know the area? http://www.thearealist.com/circle-area/how-do-you-find-the-circumference-of-a-circle-when-you-know-the-area http://www.thearealist.com/circle-area/how-do-you-find-the-circumference-of-a-circle-when-you-know-the-area#comments Fri, 25 Jun 2010 18:31:41 +0000 admin http://www.thearealist.com/circle-area/how-do-you-find-the-circumference-of-a-circle-when-you-know-the-area So if i have a circle with an area of 100 meters squared how do you find the circumference?

You need to work backwards.

You know that the area of a circle is found using the formula A = pi (3.14) x radius x radius. So, if you divide the known area (100 meters) by pi (3.14), you will get the radius squared.

Then you need to find the square root of that to have the actual length of the radius which you know is half of your diameter.

Finally, just use the diameter to determine the circumference of the circle. The formula for that is C = pi x diameter.

Now that you know how to do it, you can find the answers for yourself.

]]> http://www.thearealist.com/circle-area/how-do-you-find-the-circumference-of-a-circle-when-you-know-the-area/feed 1 How to find the area of circle if only perimeter given? http://www.thearealist.com/circle-area/how-to-find-the-area-of-circle-if-only-perimeter-given http://www.thearealist.com/circle-area/how-to-find-the-area-of-circle-if-only-perimeter-given#comments Tue, 22 Jun 2010 12:56:58 +0000 admin http://www.thearealist.com/circle-area/how-to-find-the-area-of-circle-if-only-perimeter-given Hi,
Please help me find the answer to this, getting really confused.

The perimeter of a semi circle is 49.7cm, find the area to the nearest square millimetre?

I cant work out how to get the radius or diameter to do the Area = pi x r^2 calculation.

Thanks
Just to clarify i need to find the AREA OF THE SEMI CIRCLE.
I have the PERIMETER OF THE SEMI CIRCLE

P = π r + 2 r

49.7 = r ( π + 2 )

r = 49.7 / 5.14

r = 9.67

A = π r ² / 2

A = π (9.67 ² ) / 2

A = 147 cm ²

]]> http://www.thearealist.com/circle-area/how-to-find-the-area-of-circle-if-only-perimeter-given/feed 6 What is the ratio of the area of the circle to the area of the square in this problem? http://www.thearealist.com/circle-area/what-is-the-ratio-of-the-area-of-the-circle-to-the-area-of-the-square-in-this-problem http://www.thearealist.com/circle-area/what-is-the-ratio-of-the-area-of-the-circle-to-the-area-of-the-square-in-this-problem#comments Sat, 19 Jun 2010 11:38:40 +0000 admin http://www.thearealist.com/circle-area/what-is-the-ratio-of-the-area-of-the-circle-to-the-area-of-the-square-in-this-problem From a piece of tin in the shape of a square 6 inches on a side, the largest possible circle is cut out. Of the following, the ratio of the area of the circle to the area of the original square is closest in value to…:

F. 4/5
G. 2/3
H. 3/5
J. 7/9
K. 3/4

Please explain how you found your answer. Thanks.

J. 7/9

The area of the square is one side multiplied by the other side, so it’s 6×6=36.

The area of the circle is pi times the radius squared. The radius is 3, so the radius squared is 9. 9 times pi, which is 3.14 is about 28.26.

To find the ratio of the circle to the square, you do 28/36, which reduces to 7/9.

]]> http://www.thearealist.com/circle-area/what-is-the-ratio-of-the-area-of-the-circle-to-the-area-of-the-square-in-this-problem/feed 6 What is the area of the smallest portion of the circle? http://www.thearealist.com/circle-area/what-is-the-area-of-the-smallest-portion-of-the-circle http://www.thearealist.com/circle-area/what-is-the-area-of-the-smallest-portion-of-the-circle#comments Wed, 16 Jun 2010 11:04:31 +0000 admin http://www.thearealist.com/circle-area/what-is-the-area-of-the-smallest-portion-of-the-circle Two perpendicular chords divide a circle with radius of 13 inches into four parts. If the perpendicular distances of both chords are 5 cm each from the center of the circle. Find the area of the smallest part.

The area of a quarter of the circle is 169pi/4. From this, take away two circular sectors which are each subtended by the angle arctan(5/12). The formula for the area of such sectors is (1/2)r^2theta, so each of these sectors has area (169/2)arctan(5/12). The area we now have is

169pi/4 – 169arctan(5/12).

It remains to take away two triangles, each with sides 13, 7, and 5sqrt(2). By Heron’s formula, these triangles have area 35/2. Taking away two of these, we are left with the answer

169pi/4 – 169arctan(5/12) – 35 = 31.0126.

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