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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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โˆ™ 2011-04-30 16:52:38
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Q: How do you find the radius of a circle if area is 81 pi?
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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.


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


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.


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 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


What is the area of a circle that has a radius of 9cm?

Area: pi9^2 = 81pi or 254.469 square cm rounded


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 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 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


How many square feet in a circle with the radius of 9ft?

Area of a circle = pi R2 = 81 pi = 254.47 square ft (rounded)


What is the area of a circle that has a diameter of 9 cm?

The area of a circle is figured out using the formula Now, the circle we are given has a radius of 9cm. So, the area of the circle would be: Area = 3.14 x (9)2 = 3.14 x 81 = 254.34 cm2 The area of the circle in question is 254.34 cm2


What is the area of a circle if it has a diameter which is 18 feet long?

The area of a circle is equal to πr2 where π (pi) is equal to approximately 3.142 and r represents the radius of the circle. Because the question gives you the diameter and not the radius you have to use the measurement of the diameter to calculate the radius. Remember that the radius is equal to half the diameter. So if the diameter is equal to 18 feet, then the radius of this particular circle is equal to 9 feet. Plugging this into our equation for area we get: area = π(92) area = 3.142(81) area = about 254.5 ft2 (don't forget that the answer is in squared feet not just feet)


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


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 expression can be used to find the area of a circle which is 81?

The question cannot be answered because it does not state clearly what the 81 refer to and what you are trying to find.


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 measure of the central angle with a sector area of 169.56 and a radius of 9?

Radius is 9 so area of complete circle (360o) is 81 x 3.14 ie 254.34. Angle of sector is therefore 360 x 169.56/254.34 which is 240o


What is the circumference of a circle if diameter is 162 cm?

A circle with a radius of 81 cm has a circumference of 508.94 cm


A circle is 18 feet in diameter what is the area of the circle?

Area of circle: 81*pi square feet


What is the radius if the area of the garden is 81 times pi ft?

The radius is 9 feet because pi*92 = 81*pi


If the diameter of a circle is 18 what is the area with pi?

Area of circle: 81*pi square units


What is the circumference of a circle with an area of 81?

In every circle . . .Area = (pi) x (radius)2Diameter = 2 x radiusCircumference = (pi) x diameterIn this circle, Area = (pi) R2 = 81R2 = 81/piR = sqrt( 81/pi )Diameter = 2 x sqrt( 81/pi )Circumference = (pi) x 2 x sqrt( 81/pi ) = 2 x sqrt( 81 pi ) = 18 sqrt(pi) = 31.9042 (rounded)


What is the equation of the circle with the center at the origin and a radius of 9?

x² + y² = 81.


What is the equation for a circle with a center of 0 and a radius of 9?

x2 + y2 = 81


What equation of the circle with its center at the origin and radius 9?

x2 + y2 = 81