To find the circumference of a circle, we use the formula:

$C = 2 \pi r$

where:

• $C$ is the circumference,
• $r$ is the radius of the circle,
• and $\pi$ is approximately 3.1416.

Given the radius $r = 9 \, \text{cm}$, we can substitute this into the formula:

$C = 2 \times 3.1416 \times 9$

Now, let's calculate the circumference:

$C = 2 \times 3.1416 \times 9 = 56.5488 \, \text{cm}$

Rounded to one decimal place, the circumference is:

$C \approx 56.5 \, \text{cm}$

So, the circumference of the circle is approximately 56.5 cm.

Would you like to dive deeper into any part of this? Or do you have any other questions?

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Related Questions:

1. How do you calculate the area of a circle if the radius is 9 cm?
2. What is the difference between diameter and radius in a circle?
3. How would the circumference change if the radius was doubled?
4. What is the formula for the area of a circle, and how do you use it?
5. How is the circumference of a circle related to its diameter?

Tip: When dealing with circles, remembering that the radius is half the diameter can make it easier to switch between the two when solving for circumference or area.