To determine the area of a circle with radius [tex]\( r \)[/tex] using the function [tex]\( f(r) = 3.14 r^2 \)[/tex], we need to substitute the given radius into the function.
Here is the step-by-step process:
1. Identify the given radius [tex]\( r \)[/tex]: In this problem, [tex]\( r = 5 \)[/tex].
2. Write down the function: The area function is given by [tex]\( f(r) = 3.14 r^2 \)[/tex].
3. Substitute the radius into the function:
[tex]\[
f(5) = 3.14 \times 5^2
\][/tex]
4. Calculate the square of the radius:
[tex]\[
5^2 = 25
\][/tex]
5. Multiply by 3.14:
[tex]\[
f(5) = 3.14 \times 25
\][/tex]
6. Perform the multiplication:
[tex]\[
3.14 \times 25 = 78.50
\][/tex]
Therefore, the value of [tex]\( f(5) \)[/tex] is [tex]\( 78.50 \)[/tex].
The correct answer is [tex]\( \boxed{78.50} \)[/tex].
