What is 9 times pi?

9 is an integer and pi (π) is the ratio of a circle's circumference to its diameter and is best known as 3.14. However, pi is an irrational number with an infinite number of decimals: 3. 1 4 1 5 9 2 6 5 3 5 8 9 7 9 and so on.

For most practical purposes, 9 times pi is simply 9 times 3.14 as illustrated below:

9 x 3.14 =
28.26

You can make the answer more accurate by using more decimals of pi. For example, here is 9 times pi with 12 decimal numbers:

9 x 3.141592653589 =
28.274333882301

If 9 is the diameter of a circle, then 9 times pi is the circumference of that same circle. See definitions and explanations below to find out why!

Definitions

The radius (r) of a circle is the distance from the center of the circle to the edge of the circle. The diameter (d) of a circle is the distance from one point on a circle through the center to another point on the circle. In other words, 2 times the radius equals the diameter.

Like we said above, pi is the ratio of a circle's circumference to its diameter. Therefore, we can use pi to calculate the area and circumference of a circle.

Area

The formula to calculate the area of a circle is πr^2 (pi times radius squared). If 9 is the radius, then the area of the circle is pi times 9 squared:

3.14 x 9^2 =
28.274333882301

If 9 is the diameter, then you first have to divide 9 by 2 to get the radius and then calculate pi times radius squared:

9 / 2 = 4.5
3.14 x 4.5^2 =
63.585

Circumference

The formula to calculate the circumference is 2πr (2 times pi times radius). If 9 is the radius, then the circumference of the circle is 2 times pi times 9:

2 x 3.14 x 9 =
56.52

If 9 is the diameter, then you first have to divide 9 by 2 to get the radius and then calculate 2 times pi times radius:

9 / 2 = 4.5
2 x 3.14 x 4.5 =
28.26

Note: Instead of dividing 9 by 2 above, you could also have simplified the formula because 2 times pi times radius is the same as pi times diameter. Thus, like we said at the top of this page, 9 times pi is the circumference of the circle if 9 is the diameter.

Times Pi Calculator
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What is 10 times pi?
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