The GED Math test will throw some geometry questions at you that involve three-dimensional shapes like prisms. Usually, they will be in the form of a cube or box, as in the following practice questions.

Practice Questions

  1. A cube has a surface area of 216 square inches. What is its volume in cubic inches?

    A. 6 B. 36 C. 108 D. 216

  2. If these two boxes have the same volume, what is the height of the second box?


    A. 4 B. 5 C. 8 D. 10

Answers and Explanations

  1. The correct answer is D.

    You can determine the surface area (SA) of a cube with the following equation, in which s is the length of a side:

    SA = 6s2

    You know the surface area equals 216 cubic inches, so you can substitute this into the equation for SA and solve for s:

    216 = 6s2

    Dividing both sides by 6 gives you

    36 = s2

    Hence, s = 6.

    A cube is a special type of rectangular prism in which the length (l), the width (w), and the height (h) are all equal. The volume of a rectangular prism is given by

    V = lwh

    Substituting l = 6, w = 6, and h = 6 into the equation shows the volume equals 216 cubic inches. Hence, Choice (D) is the correct answer.

  2. The correct answer is B.

    The volume of a box (rectangular prism) is V = lwh, where l is the length, w is the width, and h is the height. Set the volumes of the two boxes equal to each other and solve for h:


    Therefore, Choice (B) is the correct answer.

About This Article

This article is from the book:

About the book author:

Stuart Donnelly, PhD, earned his doctorate in mathe-matics from Oxford University at the age of 25. Since then, he has established successful tutoring services in both Hong Kong and the United States and is considered by leading educators to be one of the most experienced and qualified private tutors in the country.

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