Question

If we know r, the radius of a circle, we can find its area, A, by using the rule πr
2
.
Let’s find the output of this function, or the area of the circle, when the input
of the function, or the radius of the circle, is 12. Start by substituting 12
for the radius, r.
r
Input Output Arrow
πr
2

Input Output Arrow
A


A = πr
2

A = π(
)
2

Answer 1

To find the area \( A \) of the circle when the radius \( r \) is 12, we can use the formula:

\[
A = \pi r^2
\]

Now, we will substitute \( r \) with 12:

\[
A = \pi (12)^2
\]

Calculating \( (12)^2 \):

\[
(12)^2 = 144
\]

Now we can substitute this back into the equation for \( A \):

\[
A = \pi \times 144
\]

Thus, the area \( A \) is:

\[
A = 144\pi
\]

So the output of the function, or the area of the circle when the radius is 12, is:

\[
A = 144\pi \approx 452.39 \quad (\text{using } \pi \approx 3.14)
\]

So, filling in the information in the provided structure:

\[
\begin{array}{c|c}
\text{Input} & \text{Output} \\
\hline
r & 12 \\
\hline
A & 144\pi \\
\end{array}
\]

The final answer for the area of the circle with radius \( 12 \) is \( 144\pi \) square units.