GRE Math : Solid Geometry

Study concepts, example questions & explanations for GRE Math

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Example Questions

Example Question #2 : How To Find The Diagonal Of A Cube

You have a rectangular box with dimensions 6 inches by 6 inches by 8 inches. What is the length of the shortest distance between two non-adjacent corners of the box?

Possible Answers:

\dpi{100} \small 8\sqrt{2}

\dpi{100} \small 8

\dpi{100} \small 4\sqrt{3}

\dpi{100} \small 6\sqrt{2}

\dpi{100} \small 6

Correct answer:

\dpi{100} \small 6\sqrt{2}

Explanation:

The shortest length between any two non-adjacent corners will be the diagonal of the smallest face of the rectangular box. The smallest face of the rectangular box is a six-inch by six-inch square. The diagonal of a six-inch square is \dpi{100} \small 6\sqrt{2}.

Example Question #1 : How To Find The Diagonal Of A Cube

What is the length of the diagonal of a cube with side lengths of   each?

Possible Answers:

Correct answer:

Explanation:

The diagonal length of a cube is found by a form of the distance formula that is akin to the Pythagorean Theorem, though with an additional dimension added to it. It is:

, or , or 

Now, if the the value of  is , we get simply 

Example Question #3 : How To Find The Diagonal Of A Cube

What is the length of the diagonal of a cube that has a surface area of  ?

Possible Answers:

Correct answer:

Explanation:

To begin, the best thing to do is to find the length of a side of the cube. This is done using the formula for the surface area of a cube. Recall that a cube is made up of  squares. Therefore, its surface area is:

, where  is the length of a side.

Therefore, for our data, we have:

Solving for , we get:

This means that 

Now, the diagonal length of a cube is found by a form of the distance formula that is akin to the Pythagorean Theorem, though with an additional dimension added to it. It is:

, or , or 

Now, if the the value of  is , we get simply 

 

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

What is the volume of a rectangular box that is twice as long as it is high, and four times as wide as it is long?

Possible Answers:

4L3

8

2L2

5L

2L3

Correct answer:

2L3

Explanation:

The box is 2 times as long as it is high, so H = L/2. It is also 4 times as wide as it is long, so W = 4L. Now we need volume = L * W * H = L * 4L * L/2 = 2L3.

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

What is the volume of a cube with a surface area of  ?

Possible Answers:

Correct answer:

Explanation:

The surface area of a cube is merely the sum of the surface areas of the  squares that make up its faces. Therefore, the surface area equation understandably is:

, where  is the side length of any one side of the cube. For our values, we know:

Solving for , we get:

 or 

Now, the volume of a cube is defined by the simple equation:

For , this is:

Example Question #24 : Solid Geometry

The volume of a cube is . If the side length of this cube is tripled, what is the new volume?

Possible Answers:

Correct answer:

Explanation:

Recall that the volume of a cube is defined by the equation:

, where  is the side length of the cube. 

Therefore, if we know that , we can solve:

This means that .

Now, if we triple  to , the new volume of our cube will be:

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

What is the volume of a cube with surface area of ?

Possible Answers:

Correct answer:

Explanation:

Recall that the equation for the surface area of a cube is merely derived from the fact that the cube's faces are made up of  squares. It is therefore:

For our values, this is:

Solving for , we get:

, so 

Now, the volume of a cube is merely:

Therefore, for , this value is:

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

A cube has a volume of 64, what would it be if you doubled its side lengths?

Possible Answers:

Correct answer:

Explanation:

To find the volume of a cube, you multiple your side length 3 times (s*s*s).  

To find the side length from the volume, you find the cube root which gives you 4 

.  

Doubling the side gives you 8 

.  

The volume of the new cube would then be 512 

.

Example Question #1 : How To Find The Surface Area Of A Cube

A rectangular box is 6 feet wide, 3 feet long, and 2 feet high.  What is the surface area of this box?

Possible Answers:

72 sq ft

36 sq ft

64 sq ft

48 sq ft

22 sq ft

Correct answer:

72 sq ft

Explanation:

The surface area formula we need to solve this is 2ab + 2bc + 2ac.  So if we let a = 6, b = 3, and c = 2, then surface area:

= 2(6)(3) + 2(3)(2) +2(6)(2)

= 72 sq ft.

Example Question #2 : How To Find The Surface Area Of A Cube

What is the surface area of a rectangular box that is 3 feet high, 6 feet long, and 4 feet wide?

Possible Answers:

108

72

84

144

96

Correct answer:

108

Explanation:

Surface area of a rectangular solid

= 2lw + 2lh + 2wh

= 2(6)(4) + 2(6)(3) + 2(4)(3)

= 108

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