How does the volume of an oblique cylinder change if the radius is reduced to [tex]\frac{2}{9}[/tex] of its original size and the height is quadrupled?

A. [tex]V=\frac{2}{81} \pi r^2 h[/tex]
B. [tex]V=\frac{16}{81} \pi r^2 h[/tex]
C. [tex]V=\frac{4}{9} \pi r^2 h[/tex]
D. [tex]V=\frac{16}{9} \pi^2 h[/tex]

Please select the best answer from the choices provided.



Answer :

To determine how the volume of an oblique cylinder changes when the radius is reduced to [tex]\(\frac{2}{9}\)[/tex] of its original size and the height is quadrupled, we need to understand the formula for the volume of a cylinder.

The volume [tex]\(V\)[/tex] of a cylinder is given by:
[tex]\[ V = \pi r^2 h \][/tex]

where:
- [tex]\(r\)[/tex] is the radius of the cylinder's base,
- [tex]\(h\)[/tex] is the height of the cylinder.

Let's consider the initial volume with radius [tex]\(r\)[/tex] and height [tex]\(h\)[/tex]:
[tex]\[ V_{\text{initial}} = \pi r^2 h \][/tex]

When the radius is changed to [tex]\(\frac{2}{9}\)[/tex] of its original size:
[tex]\[ \text{New radius} = \frac{2}{9} r \][/tex]

And the height is quadrupled:
[tex]\[ \text{New height} = 4h \][/tex]

Now, we find the new volume with these changes. The new volume [tex]\(V_{\text{new}}\)[/tex] is given by:
[tex]\[ V_{\text{new}} = \pi \left(\frac{2}{9} r\right)^2 \left(4h\right) \][/tex]

First, calculate [tex]\(\left(\frac{2}{9} r\right)^2\)[/tex]:
[tex]\[ \left(\frac{2}{9} r\right)^2 = \left(\frac{2}{9}\right)^2 r^2 = \frac{4}{81} r^2 \][/tex]

Next, multiply by the new height:
[tex]\[ V_{\text{new}} = \pi \left(\frac{4}{81} r^2\right) (4h) \][/tex]
[tex]\[ V_{\text{new}} = \pi \left(\frac{4 \times 4}{81}\right) r^2 h \][/tex]
[tex]\[ V_{\text{new}} = \pi \left(\frac{16}{81}\right) r^2 h \][/tex]
[tex]\[ V_{\text{new}} = \frac{16}{81} \pi r^2 h \][/tex]

Hence, the volume of the oblique cylinder changes to:
[tex]\[ V_{\text{new}} = \frac{16}{81} \pi r^2 h \][/tex]

Therefore, the correct answer is:
[tex]\[ \boxed{B. \ \ V = \frac{16}{81} \pi r^2 h} \][/tex]