The function [tex][tex]$f(r)$[/tex][/tex] gives the area of a circle with radius [tex]$r$[/tex]. It can be written in equation form as [tex]$f(r) = 3.14 r^2$[/tex].

What is [tex][tex]$f(5)$[/tex][/tex]?

A. 246.49
B. 31.40
C. 28.14
D. 78.50



Answer :

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].