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 :

To find the volume of the cylinder in terms of [tex]\( b \)[/tex], we need to use the given formula for the volume [tex]\( V \)[/tex] of a right circular cylinder, which is:
[tex]\[ V = \pi r^2 h \][/tex]

We are given:
[tex]\[ r = 2b \][/tex]
[tex]\[ h = 5b + 3 \][/tex]

First, substitute [tex]\( r \)[/tex] into the formula:
[tex]\[ V = \pi (2b)^2 h \][/tex]

Simplify the expression within the parentheses:
[tex]\[ (2b)^2 = 4b^2 \][/tex]

Therefore:
[tex]\[ V = \pi (4b^2) h \][/tex]

Next, substitute [tex]\( h \)[/tex]:
[tex]\[ V = \pi (4b^2) (5b + 3) \][/tex]

Distribute [tex]\( 4b^2 \)[/tex] through [tex]\( (5b + 3) \)[/tex]:
[tex]\[ V = \pi (4b^2 \cdot 5b + 4b^2 \cdot 3) \][/tex]
[tex]\[ V = \pi (20b^3 + 12b^2) \][/tex]

Simplifying this expression, we get:
[tex]\[ V = 20\pi b^3 + 12\pi b^2 \][/tex]

Thus, the volume of the cylinder in terms of [tex]\( b \)[/tex] is:
[tex]\[ 20\pi b^3 + 12\pi b^2 \][/tex]

Among the given choices, the correct one is:
[tex]\[ 20 \pi b^3 + 12 \pi b^2 \][/tex]