High School

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 (7^2)(h)[/tex]



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



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

Answer :

The formula for the volume of a cone is given by

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

We are told that the volume is $147\pi$ cubic centimeters and the radius is $7$ cm. Substituting these values into the formula, we have

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

This is the correct expression that can be used to find $h$.

To verify, let’s solve for $h$:

1. Substitute $7^2 = 49$ into the equation:
$$
147\pi = \frac{1}{3} \pi (49) h.
$$

2. Multiply both sides by $3$ to eliminate the fraction:
$$
441\pi = \pi (49) h.
$$

3. Divide both sides by $\pi$:
$$
441 = 49h.
$$

4. Solve for $h$:
$$
h = \frac{441}{49} = 9.
$$

Thus, the height of the cone is $9$ cm, and the expression

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

is the correct one.