ISEE Upper Level Math : Geometry

Study concepts, example questions & explanations for ISEE Upper Level Math

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Example Questions

Example Question #1 : Finding Volume Of A Cube

If a cube is \displaystyle 8 inches tall, what is its volume?

Possible Answers:

\displaystyle 512

\displaystyle 384

\displaystyle 64

\displaystyle 500

Not enough information provided.

Correct answer:

\displaystyle 512

Explanation:

To find the volume of a cube, we multiply length by width by height, which can be represented with the forumla \displaystyle v=l\cdot w\cdot h.  Since a cube has equal sides, we can use \displaystyle 8 for all three values.

\displaystyle 8\cdot 8\cdot 8=512\: in ^{3}

Example Question #2 : Finding Volume Of A Cube

What is the volume of a cube with a side length equal to \displaystyle 7 inches?

Possible Answers:

\displaystyle 53\: in^{3}

\displaystyle 49\: in^{3}

\displaystyle 343\: in^{3}

\displaystyle 21\: in^{3}

Correct answer:

\displaystyle 343\: in^{3}

Explanation:

The volume of a a cube (or rectangular prism) can be solved using the following equation:

\displaystyle V=l\times\ w\times\ h

\displaystyle V=7in\times 7in\times 7in=343in^3

Example Question #3 : Finding Volume Of A Cube

Give the volume of a cube with surface area 150 square inches.

Possible Answers:

\displaystyle 250\sqrt{3}\textup{ in}^{3}

\displaystyle 250\textup{ in}^{3}

\displaystyle 375\textup{ in}^{3}

\displaystyle 125\sqrt{3}\textup{ in}^{3}

\displaystyle 125\textup{ in}^{3}

Correct answer:

\displaystyle 125\textup{ in}^{3}

Explanation:

Let \displaystyle s be the length of one edge of the cube. Since its surface area is 150 square inches, one face has one-sixth of this area, or \displaystyle \frac{150}{6} = 25 square inches. Therefore, \displaystyle s^{2} = 25, and \displaystyle s = 5.

The volume is the cube of this, or \displaystyle V= 5^{3}=125 cubic inches.

Example Question #3 : Cubes

What is the volume of a cube in which the edge is equal to \displaystyle \sqrt[3]{x}, and the value of \displaystyle x is:

\displaystyle x=5(4+3^{2})-3

Possible Answers:

\displaystyle 60

\displaystyle 62

\displaystyle 36

\displaystyle 61

Correct answer:

\displaystyle 62

Explanation:

First, the value of x must be solved for:

\displaystyle x=5(4+3^{2})-3

\displaystyle x=5(4+9)-3

\displaystyle x=5(13)-3

\displaystyle x=62

Given the edge of the cube is \displaystyle \sqrt[3]{x}, plugging in the value of x results in \displaystyle \sqrt[3]{62}. Thus, the area would be equal to this value cubed, which would result in 62. 

Thus, 62 is the correct answer. 

Example Question #331 : Geometry

The length of a diagonal of one face of a cube is \displaystyle N. Give the volume of the cube.

Possible Answers:

\displaystyle \frac{N^{3} \sqrt{3} }{3}

\displaystyle 3N^{3}

\displaystyle \frac{N^{3} \sqrt{2} }{2}

\displaystyle \frac{N^{3} \sqrt{3} }{9}

\displaystyle \frac{N^{3} \sqrt{2} }{4}

Correct answer:

\displaystyle \frac{N^{3} \sqrt{2} }{4}

Explanation:

Since a diagonal of a square face of the cube is\displaystyle N, each side of each square has length \displaystyle \frac{N}{\sqrt{2}}=\frac{N\sqrt{2}}{2}.

Cube this to get the volume of the cube:

\displaystyle \left (\frac{N\sqrt{2}}{2} \right )^{3}

\displaystyle = \frac{N^{3}\left ( \sqrt{2} \right )^{3} }{2^{3} }

\displaystyle = \frac{N^{3} \cdot 2 \sqrt{2} }{8}

\displaystyle = \frac{N^{3} \sqrt{2} }{4}

Example Question #332 : Geometry

The distance from one vertex of a perfectly cubic aquarium to its opposite vertex is 1.5 meters. Give the volume of the aquarium in liters.

1 cubic meter = 1,000 liters.

Possible Answers:

The correct answer is not given among the other responses.

\displaystyle 750\textup{ L}

\displaystyle 421\frac{7}{8} \textup{ L}

\displaystyle 375 \textup{ L}

\displaystyle 843\frac{3}{4} \textup{ L}

Correct answer:

The correct answer is not given among the other responses.

Explanation:

Let \displaystyle s be the length of one edge of the cube. By the three-dimensional extension of the Pythagorean Theorem, 

\displaystyle s^{2}+s^{2}+s^{2}=1.5^{2}

\displaystyle 3s^{2}=2.25

\displaystyle s^{2} = 0.75 = \frac{3}{4}

\displaystyle s = \sqrt{\frac{3}{4}} = \frac{\sqrt{3}}{\sqrt{4}}} = \frac{\sqrt{3}}{2} meters.

Cube this sidelength to get the volume:

\displaystyle s ^{3 } =\left ( \frac{\sqrt{3}}{2} \right )^{3 }= \frac{\left (\sqrt{3}\right )^{3 }}{2^{3 } } = \frac{ 3\sqrt{3} }{8 } cubic meters.

To convert this to liters, multiply by 1,000:

\displaystyle \frac{ 3\sqrt{3} }{8 } \cdot 1,000 = \frac{ 3\sqrt{3} }{8 } \cdot \frac{1,000}{1} = \frac{ 3\sqrt{3} }{1 } \cdot \frac{125}{1}= 375\sqrt{3} liters.

This is not among the given responses.

Example Question #4 : Finding Volume Of A Cube

Give the volume of a cube with surface area 240 square inches.

Possible Answers:

\displaystyle 120 \textup{ in}^{3}

\displaystyle 40 \sqrt{10} \textup{ in}^{3}

\displaystyle 120 \sqrt{10} \textup{ in}^{3}

\displaystyle 80 \textup{ in}^{3}

\displaystyle 80 \sqrt{10} \textup{ in}^{3}

Correct answer:

\displaystyle 80 \sqrt{10} \textup{ in}^{3}

Explanation:

Let \displaystyle s be the length of one edge of the cube. Since its surface area is 240 square inches, one face has one-sixth of this area, or \displaystyle \frac{240}{6} = 40 square inches. Therefore, \displaystyle s^{2} = 40, and \displaystyle s = \sqrt{40} = 2\sqrt{10}.

The volume is the cube of this, or \displaystyle V= \left ( 2\sqrt{10} \right )^{3}= 2^{3} \cdot \left ( \sqrt{10} \right )^{3}= 8 \cdot 10 \sqrt{10}= 80 \sqrt{10} cubic inches.

Example Question #11 : Solve Problems Involving Area, Volume And Surface Area Of Two And Three Dimensional Objects: Ccss.Math.Content.7.G.B.6

An aquarium is shaped like a perfect cube; the perimeter of each glass face is \displaystyle 8.4 meters. If it is filled to the recommended \displaystyle 90\% capacity, then, to the nearest hundred cubic liters, how much water will it contain? 

Possible Answers:

\displaystyle 4\textup,000\textup{ L}

\displaystyle 9\textup,300\textup{ L}

Insufficient information is given to answer the question.

\displaystyle 4\textup,400\textup{ L}

\displaystyle 8\textup,300\textup{ L}

Note:\displaystyle 1\textup{ cubic meter}= 1\textup{,}000\textup{ cubic liters}


Correct answer:

\displaystyle 8\textup,300\textup{ L}

Explanation:

A perfect cube has square faces; if a face has perimeter \displaystyle 8.4 meters, then each side of each face measures one fourth of this, or \displaystyle 2.1 meters. The volume of the tank is the cube of this, or

\displaystyle 2.1^{3} = 9.261 cubic meters.

Its capacity in liters is \displaystyle 9.261 \times 1,000 = 9,261 liters.

\displaystyle 90\% of this is 

\displaystyle 9,261 \times 0.9 = 8,335 liters. 

This rounds to\displaystyle 8\textup,300 liters, the correct response.

Example Question #333 : Geometry

Your friend gives you a puzzle cube for your birthday. If the length of one edge is 5cm, what is the volume of the cube?

Possible Answers:

\displaystyle 625cm^3

\displaystyle 125cm^3

\displaystyle 15cm^3

\displaystyle 25cm^3

Correct answer:

\displaystyle 125cm^3

Explanation:

Your friend gives you a puzzle cube for your birthday. If the length of one edge is 5cm, what is the volume of the cube?

To find the volume of a cube, use the following formula:

\displaystyle V_{cube}=s^3

Where s is the side length.

Plug in what we know to get our answer:

\displaystyle V=(5cm)^3=125cm^3

 

Example Question #2 : Cubes

A cube has a side length of \displaystyle 9 mm, what is the volume of the cube?

 

Possible Answers:

\displaystyle 72.9mm^3

\displaystyle 486mm^3

\displaystyle 81mm^3

\displaystyle 729mm^3

Correct answer:

\displaystyle 729mm^3

Explanation:

A cube has a side length of \displaystyle 9 mm, what is the volume of the cube?

To find the volume of a cube, use the following formula:

\displaystyle V_{cube}=s^3

Plug in our known side length and solve

\displaystyle V_{cube}=(9mm)^3=729mm^3

Making our answer:

\displaystyle 729mm^3

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