## How to Calculate the Circumference and Area of a Circle

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First, let's solve the expression for the circumference to get the radius. Unravel the string and measure it with a ruler.

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Mark or cut the string. Did this article help you? Read the problem carefully to find out whether it tells you the circle's radius r , diameter d , or area A , then find the section that matches your problem. The diameter is 0. When a circle is inscribed in a square , the diameter of the circle is equal to the side length of the square. Share on Facebook.

## Area of a Circle and its formula

If the word problem doesn't tell you how long the diameter is, use a different method instead. We can derive an expression for the circumference in terms of the diameter by multiplying both sides of the expression above by D, thereby isolating C.

We want to find out what the circumference is, which is C in this math problem. Radius D: It is a length and so is measured in , , or.

## Area and circumference of a rectangle

This is the part of the string that was wrapped around the circle, and since a circle's circumference is just the distance around the circle, you've found the answer! Example 2: For a circle with radius r , the following formulas are used. Pre-Algebra More about equation and inequalities Overview Fundamentals in solving Equations in one or more steps Calculating the circumference of a circle About Mathplanet.

The diameter of a bicycle wheel is 20 inches. This approach can be very helpful, especially in situations involving circles, where the radius and diameter can easily be confused. Loop the string around the circle and pull it tight.

### How to Find the Circumference of a Circle Using Its Area: 4 Steps

This number is unusual because it can't be written out as a simple fraction or decimal. When you're working on a geometric problem, though, you don't need to leave your seat. You can find the perimeter and area of the square, when at least one measure of the circle or the square is given. Interested in learning more?