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Divide the 81 pi by pi, then square root it. (Use the formula for area of circle, which gives 81pi=pi*radius squared, but rearrange to find the radius). i.e. it's the square root of 81

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The area of a circle is 81 pi square feet What is the radius?

The area is 9 feet. You find the square root of 81 which is 9. I want circumference, not area.


What is the area of a circle if the radius is 9 In?

Area of a circle of radius r = πr2Area of circle of radius 9 In = π(9)2 = π x 81 , putting value of pi we get= 3.14159625 x 81 = 254.46 sq. In


Circle A has radius 4 feet circle B has radius 9 feet What is the ratio of the area of circle A to the area of circle B?

Area(A)/ Area(B) = pi*rA2/pi*rB2 = rA2/rB2 = 16/81


If radius of a circle is diminished by 10 percent then it's area is diminished by?

Radius 10, area = 100 pi; radius 9, area = 81 pi


What is the the area of a circle with a radius of 9?

Area= pi x radius squared. So radius (9) squared = 81, 81 x 3.14. See related link for more info.


What is the area of a circle if the radius is 9?

i believe that it is 18 if the radius is 9 edit: wrong, area = pi*radius^2 so it's 3.1415926535*81=254.469


You can see a grey circle with a little white cirle in it with a radius of 3 What is the radius of the diagram's larger circle if the area of the shaded region is 72 pie?

Area of a circle with radius r = pir2Area of the largest circle = Area of the smallest circle + Area of the shaded regionSince areas of the smallest circle and the shaded region are 9pi and 72pi, the Area, A, of the largest circle isA = 9pi + 72pi = 81pi, where r2 = 81.Thus, the radius of the largest circle is 9


What is the volume of a cylinder with a radius of 9 cm and a height of 8 cm?

648pi. (pi = 3.14159...)Area of a circle = (pi) x (radius squared)= (pi)(9 squared) = (pi)81.Area of a cylinder = area of circle x height.= (pi)81 x 8= 648(pi)


What is the area of a circle with the diameter of 18?

Using 3.14 as Pi the area of circle is: 2.5434


What is the area of a circle with a diameter of 18 cm?

To find area of a circle, the formula is πr2 where π is pi. Half of the diameter is the radius (r) so you divide 18 by 2 to get the radius (9). then, you square it (multiply it by itself) giving you 81. You then multiply this by pi to get the area. The exact answer is 81π, with a good approximation of: 254.46900494077325231547411404563973361997072134938357149897


What is the diameter of a circle that has an area of 81 square inches?

radius = sq rt of (81/pi) = 5.077706252 diameter = 2*077706252 = 10.1554125 inches


What is the radius and diameter if the area of a circle is 81 square units?

pi*radius squared = 81 square units Divide both sides by pi and then square root both sides to find the value of the radius. radius = 5.077706252 or 5 units in length to one significant figure 2 times radius = diameter = 10 units in length