Pi (or ) is a number with a practically infinite number of decimal places. It represents the ratio between a circle’s circumference and its diameter. Pi is equal to 3.14159 to 5 decimal places. Using pi we can calculate the are and circumference of a circle. Here are some more decimal places of Pi:3.14159265358979323846
Using Pi to find Area
Using pi, we can find the area of a circle. There are three formulas depending on if you want to calculate the area using the diameter, radius or circumference.
Example 1Find the area of the circle with a radius of 3 cm.Using the formula for the radius, we were able to calculate the area of the circle. The area of the circle is 28.3 cm². You can usually give your answer in terms of pi (more accurate) or in decimals.
Example 2Find the area of the circle with a diameter of 5 cm.Using the formula for the diameter, we were able to calculate the area of the circle. The area of the circle is 50.3 cm². We just had to substitute the diameter into the formula.
Example 3Find the area of the circle with a circumference of 16 cm.Using the formula for the circumference, we were able to calculate the area of the circle. The area of the circle is 20.4 cm². We just had to substitute the circumference into the formula.
Using Pi to find Circumference
We can also use pi to find the circumference of a circle. Here is the formula for this.In the example underneath we have calculated the circumference of a circle using the diameter and pi.
Example 3Find the circumference of the circle.Using the formula, pi and the diameter of the circle we were able to find the circumference. The circumference of the circle is 15.7 cm.
More Maths Topics
Now you should be quite familiar with pi and how to use it to find the area and circumference of a circle. You should have a look at some other topics on Ultimate Maths such as trigonometry. You can also select another topic in our library. Please share this page if you like it or found it helpful!
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