To find the perimeter of a circle (also known as the circumference) given the radius, you can use the formula:

\[ C = 2\pi r \]

where \( C \) is the circumference and \( r \) is the radius.

Given:
\[ r = 4 \, \text{cm} \]

Plugging in the values:

\[ C = 2\pi \times 4 \]
\[ C = 8\pi \, \text{cm} \]

So, the perimeter (circumference) of the circle is:

\[ 8\pi \, \text{cm} \]
\[ \approx 25.12 \, \text{cm} \] (using \(\pi \approx 3.14\))

Would you like more details or have any questions about this solution?

Here are 5 numbered questions you might ask next:
1. How do you derive the formula for the circumference of a circle?
2. What is the area of a circle with a radius of 4 cm?
3. How would the circumference change if the radius is doubled?
4. Can you explain the relationship between the diameter and the circumference?
5. How do you find the circumference if only the diameter is given?

**Tip:** Remember that the diameter of a circle is twice the radius, and knowing this can help simplify many circle-related problems.

Discover how to calculate the perimeter (circumference) of a circle with a radius of 4 cm using the formula C = 2\pi r. This problem involves circle geometry and is suitable for students in Grades 7-9.

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