Q&A for How to Find the Circumference of a Circle Using Its Area

As explained above: (1) Divide the area by 3.14 (pi). (2) Find the square root of that number. That is the radius. (3) Multiply by 6.28 (twice pi). That's the circumference.

You're given the area. Divide by pi (3.14). That gives you the square of the radius. Find the square root. That's the radius. Double it. That's the diameter. Multiply by pi (3.14). That's the circumference.

Use a calculator, if that's not prohibited. Otherwise, see the wikiHow article Calculate a Square Root by Hand .

Divide the circumference by pi (3.14). That gives you the diameter. Divide by 2. That's the radius.

You're trying to find the area of the circle. Divide the circumference by pi. 88 / (22/7) = (88)(7/22) = (4)(7) = 28. That's the diameter. Half the diameter is 14. That's the radius. Square the radius. That's 196. Multiply by pi to get the area: (196)(22/7) = 4312 / 7 = 616 square centimeters. That's the area.

First you have to know the radius. Square the radius, then multiply by pi.

The area formula is πr². If the area is given as 4π, so in this case πr² = 4π. That means the square of the radius (r) is 4, and the radius is 2. So the diameter is 4, and the circumference (πd) is 4π. (This is the one case where the area of a circle and its circumference are equal to each other, although the units of measurement are different: for example, inches and square inches.)

All pi values are substantially the same. 3.14 is close enough for most applications.

The area of a circle is pi multiplied by the square of the radius.

Divide the circumference by pi. That's the diameter. Half of that is the radius. Square the radius. Multiply by pi. That's the area.

Divide the area by pi. Find the square root of that number. That gives you the radius of the circle. Twice the radius is the diameter.

That's correct.

Let r represent the radius (in ft) of the smaller circle. Then try to represent everything else in this problem in terms of r. The radius of the larger circle is (r+2). The areas of the circles are pi*r^2 and pi(r+2)^2. The difference is pi [(r+2)^2 - r^2] = 24 pi. The pi cancels, expand the bit in brackets. r^2 + 4r + 4 - r^2 = 24. The squared terms cancel. Divide by 4. r+1 = 6. So r = 5. the smaller radius is 5 ft and the longer one is 7 ft. Verify if you like that the areas would be 49pi and 25pi sqft. which do indeed differ by 24 sqft.

Divide the circumference by pi: that gives the diameter. Divide by 2: that's the radius. Square the radius and multiply by pi.

"Circumference" refers only to the distance measured along a curved line. If you're thinking of a semi-circle, and you want to include the diameter in the circumference measurement, you can add twice the radius to the curved-line distance.

You have to know the diameter. Multiply the diameter by pi. Then divide by 2.