21 inches
Circumference = 3.14 x diameter Diameter = radius x 2 So...... 3.14 x 132 = 414.48
21 inches
The circumference of a 21-inch circle is: 66 inches.(C = d x Pi).
By a 21-inch circle I presume you mean that the diameter is 21 inches. So the radius is half as long, 10.5 inches. The formula for the circumference of a circle is 2 pi r, where r is the radius. Pi is about 3.14. That is accurate to 2 decimals, or 3 significant digits all together. I use that approximation because the dimension we are given has 2 significant digits. So the circumference is pi times the diameter; we multiply 3.14 by 21 inches and get 65.94. To 2 significant digits, that is 66 inches. If you meant that the radius was 21 inches, then the circumference would be twice as much, or 132 inches.
The radius is 10.5
Circumference = 3.14 x diameter Diameter = radius x 2 So...... 3.14 x 132 = 414.48
Divide your circumference by pi. Diameter is 66 / 3.141592654 = 21 inches.
21 inches
The circumference of a circle with a 21 mile diameter is 66 miles (approx).
circumference is the distance around the circle, so it sounds as though you are stating the circumference in your original question; 66 inches.
The circumference of a 21-inch circle is: 66 inches.(C = d x Pi).
66 feet
By a 21-inch circle I presume you mean that the diameter is 21 inches. So the radius is half as long, 10.5 inches. The formula for the circumference of a circle is 2 pi r, where r is the radius. Pi is about 3.14. That is accurate to 2 decimals, or 3 significant digits all together. I use that approximation because the dimension we are given has 2 significant digits. So the circumference is pi times the diameter; we multiply 3.14 by 21 inches and get 65.94. To 2 significant digits, that is 66 inches. If you meant that the radius was 21 inches, then the circumference would be twice as much, or 132 inches.
The diameter is 8 feet, circumference 25.12, area 50.24
Circumference = Pi X Diameter; Pi (3.141590) x 66 = 207.3 In.
A circle with a diameter of 66 feet has an area of 3,421.19 square feet.
The radius is 10.5