Area List » circle area http://www.thearealist.com Mon, 12 Jul 2010 11:15:05 +0000 http://wordpress.org/?v=2.8.4 en hourly 1 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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]]> http://www.thearealist.com/circle-area/what-is-the-area-of-the-smallest-portion-of-the-circle/feed 1 Finding the area of a circle given the area? http://www.thearealist.com/circle-area/finding-the-area-of-a-circle-given-the-area http://www.thearealist.com/circle-area/finding-the-area-of-a-circle-given-the-area#comments Mon, 31 May 2010 04:39:31 +0000 admin http://www.thearealist.com/circle-area/finding-the-area-of-a-circle-given-the-area A circle has a circumference of 10π cm. What is the area if this circle? Justify your answer completely.

✐Explanation✐

C = 2πr (circumference of a circle)
A = πr² (area of a circle)

Use the circumference formula to determine r first. Then, use the area formula to determine the answer.

C = 10π

10π = 2πr

r = 5 cm

Substitute that to the area formula…

A = π(5)²

Therefore…

A = 25π cm²

I hope this helps!

]]> http://www.thearealist.com/circle-area/finding-the-area-of-a-circle-given-the-area/feed 1 How do you find the radius of a circle when you know the area? http://www.thearealist.com/circle-area/how-do-you-find-the-radius-of-a-circle-when-you-know-the-area http://www.thearealist.com/circle-area/how-do-you-find-the-radius-of-a-circle-when-you-know-the-area#comments Tue, 11 May 2010 07:04:05 +0000 admin http://www.thearealist.com/circle-area/how-do-you-find-the-radius-of-a-circle-when-you-know-the-area The question is: The area of a circle is proportional to the square of the radius. If the area is 113 cm^2 when the radius is 6 cm, find:
the radius of a circle with area 29 cm^2

Please show the working.. It will help me to understand it. Thanks.

A = pi r^2 = 29
r^2 = 29/pi = 9.23
r = 3.04 cm

]]> http://www.thearealist.com/circle-area/how-do-you-find-the-radius-of-a-circle-when-you-know-the-area/feed 7 what is the area of the circle of intersection of the plane and sphere? http://www.thearealist.com/circle-area/what-is-the-area-of-the-circle-of-intersection-of-the-plane-and-sphere http://www.thearealist.com/circle-area/what-is-the-area-of-the-circle-of-intersection-of-the-plane-and-sphere#comments Tue, 04 May 2010 02:48:05 +0000 admin http://www.thearealist.com/circle-area/what-is-the-area-of-the-circle-of-intersection-of-the-plane-and-sphere A sphere of radius 9 meters is intersected by a plane passing 7 meters from the sphere’s center. What is the area of the circle of intersection of the plane and sphere? Please use 3.14 for the approximation of pi.

Radius of the circle = ( 9^2 – 7^2)^0.5 = 5.657 m
area = 3.14 * 5.657^2 = 100.485 m^2………………………ans

]]> http://www.thearealist.com/circle-area/what-is-the-area-of-the-circle-of-intersection-of-the-plane-and-sphere/feed 3 How do you find the area of a circle with the middle as square shape? http://www.thearealist.com/circle-area/how-do-you-find-the-area-of-a-circle-with-the-middle-as-square-shape http://www.thearealist.com/circle-area/how-do-you-find-the-area-of-a-circle-with-the-middle-as-square-shape#comments Mon, 26 Apr 2010 05:38:51 +0000 admin http://www.thearealist.com/circle-area/how-do-you-find-the-area-of-a-circle-with-the-middle-as-square-shape Ok, so you have to find the area of the shaded shape which is the circle.The circle has a radius of 4cm and the squares’ (which is in the middle of the circle) length is 4×4. Please help me, It’s due for Monday.

Use the formula πr^2 to find the circle.

π x (4)^2 = 50.27

The area of the square can be found by 4 x 4 = 16

subtract both of them to find the shaded area.

50.27 – 16 = 34.27

]]> http://www.thearealist.com/circle-area/how-do-you-find-the-area-of-a-circle-with-the-middle-as-square-shape/feed 1 Finding the area of a circle with the radius of another tangent circle? http://www.thearealist.com/circle-area/finding-the-area-of-a-circle-with-the-radius-of-another-tangent-circle http://www.thearealist.com/circle-area/finding-the-area-of-a-circle-with-the-radius-of-another-tangent-circle#comments Tue, 20 Apr 2010 00:29:47 +0000 admin http://www.thearealist.com/circle-area/finding-the-area-of-a-circle-with-the-radius-of-another-tangent-circle The center circle has a radius of 1000 inches.
Assume that all of the other circles are tangent to the circles adjacent to them. What is the total area, in square inches, of all of the blue-coloured circles?

There are 10 medium circles around the middle and the blue small circles are in the " triangles" of the tangent circles.

Lol, I see you’re on neopets..

]]> http://www.thearealist.com/circle-area/finding-the-area-of-a-circle-with-the-radius-of-another-tangent-circle/feed 1 What is the area of a circle that circumscribes a 45-45-90 triangle if the legs measure 8 cm? http://www.thearealist.com/circle-area/what-is-the-area-of-a-circle-that-circumscribes-a-45-45-90-triangle-if-the-legs-measure-8-cm http://www.thearealist.com/circle-area/what-is-the-area-of-a-circle-that-circumscribes-a-45-45-90-triangle-if-the-legs-measure-8-cm#comments Tue, 13 Apr 2010 21:09:47 +0000 admin http://www.thearealist.com/circle-area/what-is-the-area-of-a-circle-that-circumscribes-a-45-45-90-triangle-if-the-legs-measure-8-cm What is the area of a circle that circumscribes a 45-45-90 triangle if the legs measure 8 cm?

What is the area of a circle inscribed within an isosceles right triangle whose legs measure 8cm?

What is the area of the square that can be placed within a 45-45-90 triangle whose legs measure 8cm? Two of the legs rest on the legs of the triangle and one of the other vertices touches the hypotenuse of the triangle?

1.If that triangle is inside the circle…There is a rule like…

If the angle subtended by a chord is 90 degrees then the triangle is said to be in a semicircle…So…The hypotenuse of the triangle will give U the diameter of the circle…

So…D^2 = 8^2 + 8^2
D^2 = 128
So…
r^2 = 128/4 [d = 1/2r so d^2 = 1/2r^2]

Use this to find the area of the circle…

Pi r^2 = Pi * 128/4

= Pi * 32
= 3.14*32
= 100.48 sqcm

2.There is a formula for radius of the circle…Like this in here
http://www.efunda.com/math/areas/CircleInscribeTriangleGen.cfm

Well…Area of the triangle = 1/2 * b * h here the legs are 8 cm…So area =

1/2 * 8 * 8 = 32 sqcm

k = 1/2(a + b + c)
k = 1/2(11.31 + 8 + 8)
= 27.31 / 2 = 13.665 cm

Use that formula here…

32 / 13 . 665 = 2.34 sqcm…..

3.If the legs of the right triangle have lengths a and b the side of the square has length ab/(a+b)

Use that here…8 * 8/(8 + 8) = 64 / 16 = 4cm…

Area = a^2 = 4^2 = 16 sqcm

I hope it helped U [:

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