College

The volume of a cone with a radius of 7 cm is [tex]$147 \pi$[/tex] cubic centimeters. Which expression can be used to find [tex]$h$[/tex], the height of the cone?



A. [tex]$147 \pi=\frac{1}{3}(7)(h)^2$[/tex]



B. [tex]$147 \pi=\frac{1}{3} \pi\left(7^2\right)(h)$[/tex]



C. [tex]$147 \pi=\frac{1}{3} \pi$ ch[/tex]



D. [tex]$147 \pi=\frac{1}{3} \pi(7)(h)$[/tex]

Answer :

To solve this problem, we start with the volume formula for a cone:

$$
V = \frac{1}{3}\pi r^2 h.
$$

We are given that the volume is $147\pi$ cubic centimeters and the radius is $7$ cm. Substitute these values into the formula:

$$
147\pi = \frac{1}{3}\pi (7^2) h.
$$

Notice that in this step:
- The radius $r$ is replaced by $7$, so $r^2$ becomes $7^2$.
- The constant $\pi$ is included.

This gives us the correct expression to find $h$. Therefore, the expression used to find the height is:

$$
147\pi = \frac{1}{3}\pi (7^2) h.
$$

For further clarity, if we were to solve for $h$, we would multiply both sides by $3$ and divide by $\pi(7^2)$:

$$
h = \frac{3(147\pi)}{\pi(7^2)} = \frac{441\pi}{49\pi} = 9.
$$

Thus, the height of the cone is $9$ cm.

The correct answer is the expression:

$$
147\pi = \frac{1}{3}\pi\left(7^2\right)h.
$$