how do you find the area of a circle when you have a diameter and not a radius?
603804
apply formula for it\nits easy
60098
If you are good at math and geometry, the link has a formula for exact calculation and an approximation for the diameter d if you pack two equal circles into a square with a side equal to 1.  You must scale that up by multiplying by 2' for your square.  Both centers will be on a diagonal of your square and you can use a nail and string to locate the exact centers and check out then draw the circles which will touch at the center of the square.  Good luck.
323605
Area of a circle = pi x r^2 =3.1416 x 4^2=50.265 cm^2\nArea of a circle = pi x (d^2)/4 = 3.1416 x (8^2)/4 = 50.265 cm^2\n\nCircumference of a circle = pi x diameter = 3.1416 x 8 =25.133 cm\nCircumference of a circle = pi x 2 x radius = 3.1416 x 2 x 4 =25.133 cm
1167722
areah of a circle=pie times r squared  (r is radius)\ndiameter= 2r\nso r= d/2\n\nso you do 6sqrt(3)  divided by 2\n(you get 3 times sqrt of 3)\nthen do that number sqared....times pie(3.14)\n(18 times pie...more accurate if use calculaterbut answer is 18x3.14......)
130046
Half of the diameter.\n\nor\n\nMeasure around it.  Divide that number by 3.14.  Then divide by 2.
146689
to find the area of a circle.pie r squared.r being 1/2 dia.
48612
Let r be the radius of the circle and s the length of the square's sides.\ncircle perimeter=2*pi*r, square perimeter=4*s\n2*pi*r=4*s => s=pi*r/2\ncircle area=pi*r^2, square area=s^2\ns^2=(pi*r/2)^2=pi^2*r^2/4\nBut pi<4 => pi^2*r^2/4<pi*r^2 => square area < circle area
592888
Area of the circle = pi r^2\nArea of the square = x^2\n\nThese are equal so x^2 = pi r^2\nTake the sqrt of both sides:\nx = sqrt(pi) r\nx = 1.77245385 r\n\nBut the diameter is twice the radius\nd = 2 r\n\nAs you can see d > x  because 2 > 1.77245385\n\nSo the diameter of a circle (d) would be larger than the side (x) of square with the same area.\n\nThe answer is:  The diameter of the circle
335828
The radius is half the diameter.\nThe diameter is twice the radius.\nd = 2r\n8 = 2r\nr = 8/2\nr = 4 inches
426495
It depends on what shape you want to know the area.\n\nSimple shapes have formulas. (such as a circle's area is Pi*r*r)\n\nComplex shapes which have pattern.(you know the equation of lines that form the shape), calculus is used to find the area.\n\nIf a shape is not ordinary. You should draw lines to grid it and count the area square by square.\n\n-Hope this would help-
112213
area of a circle: pi*r^2\nCircumfence: 2*pi*r
173346
For a circular cone, it's V=(1/3)*pi*h*r^2. For a cone with a non-circular base, the volume is always 1/3 the volume of the corresponding cylinder. So if the area of the base is A, the volume of the cone will be (1/3)Ah. In this, h is the vertical height of the cone and r is the radius of the circle on the base.
999585
I knew it as I did the activity.Draw a circle an divide it into 8 equal parts.It should be equal.Then cut it and stick such that the tip of one cone is up and the other is down.See that the edges stick each other close together.Do it until you finish all the 8 parts.\nNow you needed some concentration.You can see that it forms a parallelogram.Now area of parallelogram=base*height and the circumference of circle=Pi*2*radius.The base of the diagram is half the circumference that is Pi*radius,and the height will be the radius.You will also notice that Area of parallelogram=Area of circle.Therefore,Base*height=Pi *Radius *radius.so, now you have got pi*radius square.\nHope you like my answer.
838513
Sigh - first guy had it right, but didn't explain it all.  \nPi = 3.14- all you need for the problem\nRadius= half the diameter of your circle. You find the midpoint and measure from there to the side of the circle, in any direction. Most problems give you the radius. or at least show you the midpoint on the circle.\n\nSo, it is 3.14 x the amount of the radius x 2= the area of the circle.\n\nYou can do this in reverse as well, if you know the area but not the radius.
303304
Use the well known formulas that relate the radius and diameter of a circle to its circumfrence.\n\nC = pi * D\nC = 2 * pi * R\n\nFor pi, you can use 3.14 or 22/7, or whatever value your teacher wants you to use.
135768
Area = Pi times the radius squared (A=pr2)\nIf you need to know how to find the radius, go here:\n\nhttp://math.about.com/library/blcircle.htm
577740
Imagin 2 circles. \n\nTake the first which is the 10'diameter center and add 6ft (3ft walk twice) for a total od 16' diameter. So that radius is half the diameter or 8'.\n\nSo that area is A=3.14(r^2) or 3.14(8^2)=200.96\n\nThen find the area of the inside foundation that is 10' in diameter or 5' radius.\n\nso that area A=3.14(r^2) or 3.14(5^2)=78.5\n\nnow subtract the two areas to get the sidewalk area.  \n\n200.96-78.5=122.46\n\nIt may help if you draw it out. Then you can see how subtracting the foundation area from the entire area will give you the answer.