The base diameter and the height of a cone are both equal to [tex]$x$[/tex] units. Which expression represents the volume of the cone, in cubic units?

A. [tex]\pi x^2[/tex]

B. [tex]2 \pi x^3[/tex]

C. [tex]\frac{1}{3} \pi x^2[/tex]

D. [tex]\frac{1}{12} \pi x^3[/tex]



Answer :

To determine which expression represents the volume of the cone, we need to apply the formula for the volume of a cone and relate it to the given condition where both the base diameter and the height of the cone are equal to [tex]\( x \)[/tex] units.

1. Volume formula for a cone:
The volume [tex]\( V \)[/tex] of a cone is given by the formula:
[tex]\[ V = \frac{1}{3} \pi r^2 h \][/tex]
where [tex]\( r \)[/tex] is the radius of the base, and [tex]\( h \)[/tex] is the height of the cone.

2. Relate the problem's conditions to the formula:
Given that the base diameter and the height of the cone are both [tex]\( x \)[/tex] units:

- The diameter of the base [tex]\( D \)[/tex] is [tex]\( x \)[/tex], so the radius [tex]\( r \)[/tex], being half of the diameter, is:
[tex]\[ r = \frac{x}{2} \][/tex]

- The height [tex]\( h \)[/tex] of the cone is:
[tex]\[ h = x \][/tex]

3. Substitute [tex]\( r \)[/tex] and [tex]\( h \)[/tex] into the volume formula:
Substitute [tex]\( r = \frac{x}{2} \)[/tex] and [tex]\( h = x \)[/tex] into the volume formula [tex]\( V = \frac{1}{3} \pi r^2 h \)[/tex]:
[tex]\[ V = \frac{1}{3} \pi \left( \frac{x}{2} \right)^2 x \][/tex]

4. Simplify the expression:
- Calculate [tex]\( \left( \frac{x}{2} \right)^2 \)[/tex]:
[tex]\[ \left( \frac{x}{2} \right)^2 = \frac{x^2}{4} \][/tex]

- Substitute [tex]\( \frac{x^2}{4} \)[/tex] into the volume formula:
[tex]\[ V = \frac{1}{3} \pi \cdot \frac{x^2}{4} \cdot x \][/tex]

- Combine the [tex]\( x \)[/tex] terms:
[tex]\[ V = \frac{1}{3} \pi \cdot \frac{x^2}{4} \cdot x = \frac{1}{3} \cdot \frac{\pi x^3}{4} = \frac{\pi x^3}{12} \][/tex]

5. Conclusion:
The simplified expression that represents the volume of the cone is:
[tex]\[ \frac{1}{12} \pi x^3 \][/tex]

Thus, the correct expression is:
[tex]\[ \boxed{\frac{1}{12} \pi x^3} \][/tex]