Pre-Algebra : Volume of a Pyramid

Study concepts, example questions & explanations for Pre-Algebra

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Example Questions

Example Question #1 : Volume

Principal O'Shaughnessy has a paperweight in the shape of a pyramid with a square base.  If one side of the base has a length of 4cm and the height of the paperweight is 6cm, what is the volume of the paperweight?

Possible Answers:

\displaystyle 32cm^3

\displaystyle 192cm^3

\displaystyle 576cm^3

\displaystyle 96cm^3

\displaystyle 48cm^3

Correct answer:

\displaystyle 32cm^3

Explanation:

We begin by recalling the volume of a pyramid.

\displaystyle V=\frac{1}{3}Ah 

where \displaystyle A is the area of the base and \displaystyle h is the height.

Since the base is a square, we can find the area by squaring the length of one of the sides.

\displaystyle A=4^2=16

Given the height is 6cm, we can now calculate the volume.

\displaystyle V=\frac{1}{3}(16)(6)=32

Since all of the measurements were in centimeters, our volume will be in cubic centimeters. 

Therefore, the volume of Principal O'Shaughnessy's paperweight is \displaystyle 32cm^3.

Example Question #1 : Volume Of A Pyramid

The volume of a square pyramid is \displaystyle 162 m^{3}. If a side of the square base measures \displaystyle 9m. What is the height of the pyramid?

Possible Answers:

\displaystyle 4.5m

\displaystyle 9m

\displaystyle 6m

\displaystyle 5m

\displaystyle 7.5m

Correct answer:

\displaystyle 6m

Explanation:

The formula for the volume of a pyramid is \displaystyle \frac{\left ( B \times h\right )}{3}, where \displaystyle B is the area of the base and \displaystyle h is the height.

 Using this formula, 

\displaystyle B = Area of the base, which is nothing but area of square with side \displaystyle 9m\displaystyle 9m \times 9m = 81 m^{2}

Now, \displaystyle \frac{81m^{2} \times h}{3} = 162 m^{3} when simplified, you get \displaystyle 6m.

Hence, the height of the pyramid is \displaystyle 6m.

Example Question #1 : Volume Of A Pyramid

A pyramid has height 4 feet. Its base is a square with sidelength 3 feet. Give its volume in cubic inches.

Possible Answers:

\displaystyle 62,208 \textrm{ in}^{3}

\displaystyle 5,184\textrm{ in}^{3}

\displaystyle 124,416\textrm{ in}^{3}

\displaystyle 31,104\textrm{ in}^{3}

\displaystyle 20,736 \textrm{ in}^{3}

Correct answer:

\displaystyle 20,736 \textrm{ in}^{3}

Explanation:

Convert each measurement from inches to feet by multiplying it by 12:

Height: 4 feet = \displaystyle 4 \times 12 = 48 inches

Sidelength of the base: 3 feet = \displaystyle 3 \times 12 = 36 inches

The volume of a pyramid is 

\displaystyle V = \frac{1}{3} Bh

Since the base is a square, we can replace \displaystyle B = s^{2}:

\displaystyle V = \frac{1}{3} s ^{2}h

Substitute \displaystyle s=36, h = 48

\displaystyle V = \frac{1}{3} \cdot 36 ^{2}\cdot 48

\displaystyle V =20,736

The pyramid has volume 20,736 cubic inches.

 

Example Question #1 : Solid Geometry

The height of a right pyramid is \displaystyle 2 feet. Its base is a square with sidelength \displaystyle 3 feet. Give its volume in cubic inches.

Possible Answers:

\displaystyle 15,552 \textrm{ in}^{3}

\displaystyle 41,472 \textrm{ in}^{3}

\displaystyle 10,368 \textrm{ in}^{3}

\displaystyle 62,208\textrm{ in}^{3}

\displaystyle 31,104 \textrm{ in}^{3}

Correct answer:

\displaystyle 10,368 \textrm{ in}^{3}

Explanation:

Convert each of the measurements from feet to inches by multiplying by \displaystyle 12.

Height: \displaystyle 2 \times 12 = 24 inches

Sidelength of base: \displaystyle 3 \times 12 = 36 inches

The base of the pyramid has area 

\displaystyle B = s^{2} = 36^{2} = 1,296 square inches.

Substitute \displaystyle B = 1,296, h = 24  into the volume formula:

\displaystyle V = \frac {1}{3} Bh

\displaystyle V = \frac {1}{3} \cdot 1,296 \cdot 24 =10,368 cubic inches

Example Question #2 : Solid Geometry

The height of a right pyramid and the sidelength of its square base are equal. The perimeter of the base is 3 feet. Give its volume in cubic inches.

Possible Answers:

\displaystyle 27 \textrm{ in}^{3}

\displaystyle 243 \textrm{ in}^{3}

\displaystyle 729 \textrm{ in}^{3}

\displaystyle 81 \textrm{ in}^{3}

\displaystyle 576 \textrm{ in}^{3}

Correct answer:

\displaystyle 243 \textrm{ in}^{3}

Explanation:

The perimeter of the square base, \displaystyle 3 feet, is equivalent to \displaystyle 3 \times 12 = 36 inches; divide by \displaystyle 4 to get the sidelength of the base - and the height: \displaystyle 36 \div 4 = 9 inches. 

The area of the base is therefore \displaystyle B = s^{2} = 9^{2} = 81 square inches. 

In the formula for the volume of a pyramid, substitute \displaystyle B = 81,h=9:

\displaystyle V = \frac{1}{3} Bh = \frac{1}{3}\cdot 81 \cdot 9 = 243 cubic inches.

Example Question #3 : Solid Geometry

What is the volume of a pyramid with the following measurements?

\displaystyle length=7; width=6;height=9;slant\ length=11

Possible Answers:

\displaystyle 462

\displaystyle 378

\displaystyle 126

\displaystyle 154

Correct answer:

\displaystyle 126

Explanation:

The volume of a pyramid can be determined using the following equation:

\displaystyle V=\frac{1}{3}lwh=\frac{1}{3}(7)(6)(9)=126

Example Question #2 : Volume Of A Pyramid

The pyramid has a length, width, and height of \displaystyle 2,4,6 respectively.  What is the volume of the pyramid?

Possible Answers:

\displaystyle 48

\displaystyle 32

\displaystyle 26

\displaystyle 16

\displaystyle 24

Correct answer:

\displaystyle 16

Explanation:

Write the formula for the volume of a pyramid.

\displaystyle V=\frac{1}{3} (L\times W\times H)

Substitute the dimensions and solve.

\displaystyle V=\frac{1}{3} (2\times 4\times 6) = \frac{1}{3}(48)=16

Example Question #3 : Volume Of A Pyramid

If the base area of the pyramid is \displaystyle 2, and the height is \displaystyle 3, what is the volume of the pyramid?

Possible Answers:

\displaystyle 9

\displaystyle 6

\displaystyle 8

\displaystyle 4

\displaystyle 2

Correct answer:

\displaystyle 2

Explanation:

Write the volume formula for the pyramid.

\displaystyle V=\frac{1}{3} (L\times W\times H)

The base area is represented by \displaystyle L\times W.

Substitute the knowns into the formula.

\displaystyle V=\frac{1}{3} (2\times 3) = \frac{1}{3} (6) =2

Example Question #4 : Volume Of A Pyramid

Find the volume of a pyramid with a length of 4, width of 7, and a height of 3.

Possible Answers:

\displaystyle 56

\displaystyle 28

\displaystyle 48

\displaystyle 96

\displaystyle 84

Correct answer:

\displaystyle 28

Explanation:

Write the formula to find the area of a pyramid.

\displaystyle V=\frac{1}{3} (L\times W \times H)

Substitute the dimensions.

\displaystyle V=\frac{1}{3} (4\times 7\times 3) = 28

Example Question #5 : Volume Of A Pyramid

Find the volume of a pyramid if the length, base, and height are  respectively.

Possible Answers:

\displaystyle \frac{8000}{3}

\displaystyle \frac{400}{3}

\displaystyle 500

\displaystyle \frac{800}{3}

\displaystyle 400

Correct answer:

\displaystyle \frac{8000}{3}

Explanation:

Write the formula for the volume of a pyramid.

\displaystyle V=\frac{1}{3} (LWH)

Substitute the dimensions and solve for the volume.

\displaystyle V=\frac{1}{3} (10)(20)(40) = \frac{8000}{3}

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