Its just the area of a circle 21 inches or 21 centimeters? area of a circle is (pi)*r2 where pi = 3.1415.... and r = radius thus A = (3.1415)*(diameter/2)2 u can figure out the answer from that with a calculator
If radius=21 ft, then diameter = 2*radius = 42 ft
the radius is 10.5 inches. * * * * * Wrong! Circumference = 2*pi*Radius Or, Radius = Circumference/(2*pi) So circumference = 21 inches implies radius = 3.34 inches (to 3 sf)
Well, darling, the circumference of a circle is calculated using the formula C = 2πr. So, with a radius of 21 cm, you just plug that bad boy in and get C = 2 x π x 21 = 132 cm. Voilà, there you have it!
Well, let's imagine that circle as a happy little friend on our canvas. To find the square footage, we first need to find the radius by dividing the diameter by 2. So, with a 42-inch diameter, the radius would be 21 inches. Then we can use the formula for the area of a circle, which is π times the radius squared. Just remember, there are about 0.00595 square feet in one square inch, so you can use that to convert your final answer.
About 1385.44cm2
The area of a circle of radius 21 is 1386
A circle with a radius of 21 cm has an area of ~1,385.44 square cm
Its just the area of a circle 21 inches or 21 centimeters? area of a circle is (pi)*r2 where pi = 3.1415.... and r = radius thus A = (3.1415)*(diameter/2)2 u can figure out the answer from that with a calculator
Using 3.14 as Pi the area of circle is: 1384.74
A circle with a radius of 21 units has an area of 1,385.44 square units.
Area = pi*212
Using 3.14 as Pi the area of circle is: 1384.74
About 1385.44cm2
If the area is a circle and the radius of the circle is 21 miles, the distance around the circle (circumference) is 131.95 miles. The area of that circle is 1,385.4 square miles.
A circle with a radius of 21 yards has an area of 1,385.44 square yards.
The area is 441 times pi.