The formula for the volume of a right circular cylinder is [tex]V=\pi r^2 h[/tex]. If [tex]r=2b[/tex] and [tex]h=5b+3[/tex], what is the volume of the cylinder in terms of [tex]b[/tex]?

A. [tex]10 \pi b^2 + 6 \pi b[/tex]
B. [tex]20 \pi b^3 + 12 \pi b^2[/tex]
C. [tex]20 \pi^2 b^3 + 12 \pi^2 b^2[/tex]
D. [tex]50 \pi b^3 + 20 \pi b^2 + 90 \pi b[/tex]



Answer :

Sure, let's break this down step by step using the formula for the volume of a right circular cylinder, which is given by:

[tex]\[ V = \pi r^2 h \][/tex]

Given:
- [tex]\( r = 2b \)[/tex] (radius in terms of [tex]\( b \)[/tex])
- [tex]\( h = 5b + 3 \)[/tex] (height in terms of [tex]\( b \)[/tex])

Now, let's substitute [tex]\( r = 2b \)[/tex] and [tex]\( h = 5b + 3 \)[/tex] into the volume formula.

1. Substitute the radius [tex]\( r = 2b \)[/tex] into the formula [tex]\( \pi r^2 h \)[/tex]:
[tex]\[ V = \pi (2b)^2 h \][/tex]

2. Calculate [tex]\( (2b)^2 \)[/tex]:
[tex]\[ (2b)^2 = 4b^2 \][/tex]
So now we have:
[tex]\[ V = \pi (4b^2) h \][/tex]

3. Substitute the height [tex]\( h = 5b + 3 \)[/tex] into the formula:
[tex]\[ V = \pi (4b^2)(5b + 3) \][/tex]

4. Distribute [tex]\( 4b^2 \)[/tex] through the term [tex]\( (5b + 3) \)[/tex]:
[tex]\[ V = \pi (4b^2 \cdot 5b + 4b^2 \cdot 3) \][/tex]

5. Perform the multiplications:
[tex]\[ 4b^2 \cdot 5b = 20b^3 \][/tex]
[tex]\[ 4b^2 \cdot 3 = 12b^2 \][/tex]

6. Add the two products together within the same parentheses:
[tex]\[ V = \pi (20b^3 + 12b^2) \][/tex]

7. Factor the [tex]\(\pi\)[/tex] back into the equation:
[tex]\[ V = 20\pi b^3 + 12\pi b^2 \][/tex]

So, the volume of the cylinder in terms of [tex]\( b \)[/tex] is [tex]\(\boxed{20 \pi b^3 + 12 \pi b^2}\)[/tex].

That matches with the given choices, so the correct answer from the options provided is:

[tex]\[ \boxed{20 \pi b^3 + 12 \pi b^2} \][/tex]