You work for a store that sells built-to-order water reservoirs. Your manager asks you to visit a small business to measure a damaged conical water reservoir for replacement. The label on the water reservoir indicates the following specifications: the height is 8.5 feet, and, when full, the water reservoir holds 225 cubic feet of water.

Which formula will determine the radius of the water reservoir? Rounded to the nearest hundredth of a foot, what is the radius of the water reservoir?

A. [tex]r=\frac{\sqrt{V}}{3.14 h}, r =0.56[/tex] feet
B. [tex]r=\frac{3 \sqrt{V}}{3.14 h}, r =1.69[/tex] feet
C. [tex]r=\sqrt{\frac{3 V}{3.14 h}}, r=5.03[/tex] feet
D. [tex]r=\sqrt{\frac{3 V-h}{3.14}}, r=8.22[/tex] feet
E. [tex]r=\sqrt{\frac{V}{3.14 h}}(3), r=8.71[/tex] feet

Answer :

To determine the radius of the conical water reservoir, we need to use the formula for the volume of a cone. The volume [tex]\( V \)[/tex] of a cone can be calculated using the formula:

[tex]\[ V = \frac{1}{3} \pi r^2 h \][/tex]

Where:
- [tex]\( V \)[/tex] is the volume
- [tex]\( r \)[/tex] is the radius of the base
- [tex]\( h \)[/tex] is the height of the cone
- [tex]\( \pi \)[/tex] is approximately 3.14

From the problem, we know:
- The volume [tex]\( V = 225 \)[/tex] cubic feet
- The height [tex]\( h = 8.5 \)[/tex] feet

Our goal is to solve for [tex]\( r \)[/tex], the radius. First, rearrange the formula to solve for [tex]\( r^2 \)[/tex]:

[tex]\[ V = \frac{1}{3} \pi r^2 h \][/tex]

Multiply both sides by 3 to get rid of the fraction:

[tex]\[ 3V = \pi r^2 h \][/tex]

Now, solve for [tex]\( r^2 \)[/tex]:

[tex]\[ r^2 = \frac{3V}{\pi h} \][/tex]

Take the square root of both sides to solve for [tex]\( r \)[/tex]:

[tex]\[ r = \sqrt{\frac{3V}{\pi h}} \][/tex]

Substitute the values we have for [tex]\( V \)[/tex], [tex]\( h \)[/tex], and [tex]\( \pi \)[/tex]:

[tex]\[ r = \sqrt{\frac{3 \times 225}{3.14 \times 8.5}} \][/tex]

After calculating, you find that the radius [tex]\( r \)[/tex] is approximately 5.03 feet when rounded to the nearest hundredth.

So, the correct formula from the options given is:

[tex]\[ r = \sqrt{\frac{3 V}{3.14 h}}, r = 5.03 \text{ feet} \][/tex]

This result matches the one provided, ensuring accuracy in determining the radius of the conical water reservoir.