The formula for the area of a circle is πr². For this particular circle, the area is 81π, so 81π = πr². Divide both sides by π and we are left with r²=81. Take the square root of both sides to find r=9. The formula for the circumference of the circle is 2πr = 2π(9) = 18π. The correct answer is 18π.

The formula for the area of a circle isA=πr².

We are given the area, and by substitution we know that 13π=πr².

We divide out theπand are left with 13 =r².

We take the square root ofrto find thatr= √13.

We find the circumference of the circle with the formulaC= 2πr.

We then plug in our values to findC= 2√13π.

首先你必须画出图。t的对角线he rectangle is also the diameter of the circle. The diagonal is the hypotenuse of a multiple of 2 of a 3,4,5 triangle, and therefore is 10.
Circumference =π *diameter = 10π.

The shape of the garden consists of a rectangle and two semi-circles. Since they are building a fence we need to find the perimeter. The perimeter of the length of the rectangle is 24. The perimeter or circumference of the circle can be found using the equation C=2π(r), where r= the radius of the circle. Since we have two semi-circles we can find the circumference of one whole circle with a radius of 4, which would be 8π.

We first must calculate the distance between these two points. Recall that the distance formula is:√((x₂- x₁)²+ (y₂- y₁)²)

For us, it is therefore: √((4 - 2)²+ (6 - 5)²) = √((2)²+ (1)²) = √(4 + 1) = √5

If d = √5, the circumference of our circle isπd, orπ√5.

If the radius is 18 inches, the diameter is 3 feet. The circumference of the tire is therefore 3π by C=d(π). After 200 revolutions, the tire and car have gone 3π x 200 = 600π feet.

The radius is 3. Yielding a circumference of.

Begin by solving for the circumference of the circle. Use the area of the circle, which is given, and the equation for the area of a circle to determine the radius of the circle:

=

Divide both sides by.

=

年代olve for:

圆的半径是6。现在发现环ference.

Circumference is equal to 2 times the radius multiplied by.

Now that we have the circumference, divide by 6 to find the length of one of the slices of the circle:

The arc length of one of the slices of the circle is.

In order to solve this question, first calculate the length of each side of the room.

The length of each side of the room is also equal to the length of the diameter of the largest circular rug that can fit in the room. Since, the circumference is simply