High School Math : How to find the volume of a cylinder

Study concepts, example questions & explanations for High School Math

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Example Questions

Example Question #1 : Cylinders

What is the volume of a cylinder with a radius of 2 and a length that is three times as long as its diameter?

Possible Answers:

\(\displaystyle 16\pi\)

\(\displaystyle 48\pi\)

\(\displaystyle 14\)

\(\displaystyle 12\pi\)

\(\displaystyle 24\)

Correct answer:

\(\displaystyle 48\pi\)

Explanation:

The volume of a cylinder is the base multiplied by the height or length.  The base is the area of a circle, which is \(\displaystyle \pi r^{2}\).  Here, the radius is 2.  The diameter is 4. Three times the diameter is 12.  The height or length is 12. So, the answer is  \(\displaystyle 48\pi\).

Example Question #1 : Cylinders

A water glass has the shape of a right cylinder. The glass has an interior radius of 2 inches, and a height of 6 inches. The glass is 75% full. What is the volume of the water in the glass (in cubic inches)?

Possible Answers:

\(\displaystyle 36 \pi\)

\(\displaystyle 18 \pi\)

\(\displaystyle 24 \pi\)

\(\displaystyle 12 \pi\)

\(\displaystyle 9 \pi\)

Correct answer:

\(\displaystyle 18 \pi\)

Explanation:

The volume of a right cylinder with radius \(\displaystyle r=2\) and height \(\displaystyle h=6\) is:

 \(\displaystyle \pi r^2 h = \pi (2)^2 (6) = 24 \pi\)

Since the glass is only 75% full, only 75% of the interior volume of the glass is occupied by water. Therefore the volume of the water is:

\(\displaystyle 24 \pi \times ( 75 / 100 ) = 24 \pi (0.75) = 18 \pi\)

Example Question #1 : How To Find The Volume Of A Cylinder

A circle has a circumference of 4\pi\(\displaystyle 4\pi\) and it is used as the base of a cylinder. The cylinder has a surface area of 16\pi\(\displaystyle 16\pi\). Find the volume of the cylinder.

Possible Answers:

4\pi\(\displaystyle 4\pi\)

2\pi\(\displaystyle 2\pi\)

10\pi\(\displaystyle 10\pi\)

8\pi\(\displaystyle 8\pi\)

6\pi\(\displaystyle 6\pi\)

Correct answer:

8\pi\(\displaystyle 8\pi\)

Explanation:

Using the circumference, we can find the radius of the circle. The equation for the circumference is 2\pi r\(\displaystyle 2\pi r\); therefore, the radius is 2.

Now we can find the area of the circle using \pi r^{2}\(\displaystyle \pi r^{2}\). The area is 4\pi\(\displaystyle 4\pi\).

Finally, the surface area consists of the area of two circles and the area of the mid-section of the cylinder: 2\cdot 4\pi +4\pi h=16\pi\(\displaystyle 2\cdot 4\pi +4\pi h=16\pi\), where h\(\displaystyle h\) is the height of the cylinder.

Thus, h=2\(\displaystyle h=2\) and the volume of the cylinder is 4\pi h=4\pi \cdot 2=8\pi\(\displaystyle 4\pi h=4\pi \cdot 2=8\pi\).

Example Question #1 : How To Find The Volume Of A Cylinder

What is the volume of a cylinder that has a base with a radius of 5 and a height of 52?

Possible Answers:

\(\displaystyle 77\pi\)

\(\displaystyle 1300\pi\)

\(\displaystyle 230\)

\(\displaystyle 1300\)

Correct answer:

\(\displaystyle 1300\pi\)

Explanation:

To find the volume of a cylinder we must know the equation for the volume of a cylinder which is \(\displaystyle Volume\:of\:cylinder= r^{2}*\pi*height\:of\:cylinder\)

In this example the height is 52 and the radius is 5 which we plug into our equation which will look like this \(\displaystyle Volume\:of\:cylinder= 5^{2}*\pi*52\)

We then square the 5 to get \(\displaystyle Volume=25*\pi*52\)

Then perform multiplication to get \(\displaystyle Volume=1300\pi\)

Example Question #761 : Geometry

What is the surface area of a cylinder with a radius of 2 cm and a height of 10 cm?

Possible Answers:

48π cm2

32π cm2

36π cm2

56π cm2

40π cm2

Correct answer:

48π cm2

Explanation:

SAcylinder = 2πrh + 2πr2 = 2π(2)(10) + 2π(2)2 = 40π + 8π = 48π cm2

 

Example Question #1961 : High School Math

A cylinder has a radius of \(\displaystyle r=3cm\) and a height of \(\displaystyle h=27cm\).  What is its volume?

Possible Answers:

\(\displaystyle 243\pi cm^{3}\)

\(\displaystyle \dpi{100} 234\pi cm^{3}\)

\(\displaystyle \dpi{100} 162\pi cm^{3}\)

\(\displaystyle \dpi{100} 162\pi cm^{3}\)

\(\displaystyle \dpi{100} 81\pi cm^{3}\)

Correct answer:

\(\displaystyle 243\pi cm^{3}\)

Explanation:

In order to calculate the volume of a cylinder, we must utilize the formula \(\displaystyle V=\pi r^{2}h\). We were given the radius, \(\displaystyle \dpi{100} r=3cm\), and the height, \(\displaystyle \dpi{100} h=27cm\).

Insert the known variables into the formula and solve for volume \(\displaystyle \dpi{100} V\).

\(\displaystyle V=\pi *(3cm)^{2}*27cm\)

\(\displaystyle V=\pi*9cm^{2}*27cm\)

\(\displaystyle V=243\pi cm^{3}\)

In essence, we find the area of the cylinder's circular base, \(\displaystyle \dpi{100} A=\pi r^{2}\), and multiply it by the height.

 

Example Question #2 : How To Find The Volume Of A Cylinder

A cylinder has a radius of \(\displaystyle \dpi{100} r=\pi\) and a height of \(\displaystyle \dpi{100} h=10\).  What is its volume

Possible Answers:

Not enough information to solve.

\(\displaystyle 10\pi^{2}\)

\(\displaystyle 10\pi^{4}\)

\(\displaystyle 10\pi^{3}\)

\(\displaystyle \sqrt{10\pi}\)

Correct answer:

\(\displaystyle 10\pi^{3}\)

Explanation:

In order to calculate the volume of a cylinder, we must utilize the formula \(\displaystyle V=\pi r^{2}h\). We were given the radius, \(\displaystyle \dpi{100} \dpi{100} r=\pi\), and the height, \(\displaystyle \dpi{100} \dpi{100} h=10\).

Insert the known variables into the formula and solve for volume \(\displaystyle \dpi{100} V\).

\(\displaystyle \dpi{100} V=\pi *(\pi)^{2}*10\)

\(\displaystyle \dpi{100} V=\pi*\pi^{2}*10\)

\(\displaystyle \dpi{100} V=10\pi^{3}\)

In essence, we find the area of the cylinder's circular base, \(\displaystyle \dpi{100} A=\pi r^{2}\), and multiply it by the height.

Example Question #3 : How To Find The Volume Of A Cylinder

Cylinder_with_a_sphere

A sphere with a radius of \(\displaystyle r=2cm\) is circumscribed in a cylinder. What is the cylinder's volume?

Possible Answers:

\(\displaystyle 27.28cm^{3}\)

\(\displaystyle 50.27cm^{3}\)

\(\displaystyle \dpi{100} 27.50cm^{3}\)

Not enough information to solve

\(\displaystyle \dpi{100} 28.27cm^{3}\)

Correct answer:

\(\displaystyle 50.27cm^{3}\)

Explanation:

In order to solve this problem, one key fact needs to be understood.  A sphere will take up exactly \(\displaystyle \frac{2}{3}\) of the volume of a cylinder in which it is circumscribed. Therefore, if we find the volume of the sphere we can then solve for the volume of the cylinder.

First, we need to find the volume of the sphere.

\(\displaystyle \dpi{100} V=\frac{4}{3}\pi (2cm)^{3}\)

\(\displaystyle \dpi{100} \dpi{100} V_{sphere}=10\frac{2}{3}\pi cm^{3}\)

This equals \(\displaystyle \frac{2}{3}\) of the volume of the cylinder. Therefore,

\(\displaystyle \dpi{100} V_{cylinder}=\frac{3}{2}(10\frac{2}{3}\pi cm^{3})\)

\(\displaystyle \rightarrow 50.27cm^{3}\)

Example Question #111 : Solid Geometry

Calculate the volume of a cylinder with a height of six, and a base with a radius of three.

Possible Answers:

\(\displaystyle 18\)

\(\displaystyle 54\)

\(\displaystyle 54\pi\)

\(\displaystyle 18\pi\)

Correct answer:

\(\displaystyle 54\pi\)

Explanation:

The volume of a cylinder is give by the equation \(\displaystyle \small V=\pi r^2h\).

In this example, \(\displaystyle \small h=6\) and \(\displaystyle \small r=3\).

\(\displaystyle V=\pi(3)^2(6)\)

\(\displaystyle V=\pi(9)(6)=54\pi\)

Example Question #1 : How To Find The Volume Of A Cylinder

What is the volume of a cylinder with a circular side with a radius of \(\displaystyle 7\) and a length of \(\displaystyle 12\)?

Possible Answers:

\(\displaystyle 588\pi\)

\(\displaystyle 84\pi\)

\(\displaystyle 168\pi\)

\(\displaystyle 334\pi\)

Correct answer:

\(\displaystyle 588\pi\)

Explanation:

To find the volume of a cylinder we must know the equation for the volume of a cylinder which is

In this example the length is \(\displaystyle 12\) and the radius is \(\displaystyle 7\) so our equation will look like this \(\displaystyle V=(12)(\pi)(7^{2})\)

We then square the \(\displaystyle 7\) to get \(\displaystyle 7^{2}=49\)

Then perform multiplication to get \(\displaystyle (49)(12)(\pi)=588\pi\)

The answer is \(\displaystyle 588\pi\).

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