GMAT Math : Rectangular Solids & Cylinders

Study concepts, example questions & explanations for GMAT Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #3 : Calculating The Volume Of A Prism

A given cylinder has circular bases of radius \displaystyle 6 and height \displaystyle 12. What is the volume of the cylinder?

Possible Answers:

\displaystyle 72\pi

\displaystyle 432\pi

\displaystyle 36\pi

\displaystyle 18\pi

\displaystyle 144\pi

Correct answer:

\displaystyle 432\pi

Explanation:

The volume \displaystyle V of a given cylinder is the product of its base area \displaystyle (A) and height \displaystyle (h), or \displaystyle V=Ah. Since the circular base area \displaystyle A=\pi r^{2}, we can substitute and plug in the values provided:

\displaystyle V=Ah

\displaystyle V=(\pi r^{2})h

\displaystyle V=(\pi (6)^{2})(12)

\displaystyle V=432\pi

Example Question #551 : Geometry

A given rectangular prism has a length of \displaystyle 7cm, a width of \displaystyle 5cm, and a height of \displaystyle 9cm. What is the volume of the prism?

Possible Answers:

Not enough information provided.

\displaystyle 52cm^{3}

\displaystyle 315cm^{3}

\displaystyle 21cm^{3}

\displaystyle 108cm^{3}

Correct answer:

\displaystyle 315cm^{3}

Explanation:

The volume \displaystyle V of a given rectangular prism is the product of its length \displaystyle (l), width \displaystyle (w), and height \displaystyle (h), or \displaystyle V=lwh. Plugging in the values provided:

\displaystyle V=(7cm)(5cm)(9cm)

\displaystyle V=315cm^{3}

Example Question #791 : Problem Solving Questions

A given rectangular prism has a length of \displaystyle 10cm, a width of \displaystyle 5cm, and a height of \displaystyle 20cm. What is its volume?

Possible Answers:

\displaystyle 1000cm^{3}

\displaystyle 700cm^{3}

\displaystyle 35cm^{3}

\displaystyle 100cm^{3}

\displaystyle 500cm^{3}

Correct answer:

\displaystyle 1000cm^{3}

Explanation:

The volume \displaystyle V of a given rectangular prism is the product of its length \displaystyle (l), width \displaystyle (w), and height \displaystyle (h), or \displaystyle V=lwh. Plugging in the values provided:

\displaystyle V=(10cm)(5cm)(20cm)

\displaystyle V=1000cm^{3}

Example Question #23 : Prisms

Ron is making a wooden chest. The chest needs to measure 45 inches by 72 inches by 36 inches. What volume will the chest be able to hold in cubic feet?

Possible Answers:

\displaystyle 153

\displaystyle 36

\displaystyle 54

\displaystyle 67.5

Correct answer:

\displaystyle 67.5

Explanation:

Because we are asked for an answer in cubic feet, convert all measurments to feet right away

45 inches: 3.5 feet

72 inches: 6 feet

36 inches: 3 feet

Volume of a rectangular prism is given by: 

V=l*w*h

So

V=3*6*3.5=67.5 ft^3

Example Question #1 : Calculating The Diagonal Of A Prism

If a rectangular prism has a length of  \displaystyle 6,  a width of  \displaystyle 4,  and a height of  \displaystyle 3,  what is the length of its diagonal?

Possible Answers:

\displaystyle \sqrt{71}

\displaystyle 15\sqrt{2}

\displaystyle \sqrt{61}

\displaystyle 2\sqrt{13}

\displaystyle 9

Correct answer:

\displaystyle \sqrt{61}

Explanation:

The diagonal of a rectangular prism can be thought of as the hypotenuse of a right triangle formed by the height of the prism and the diagonal of its bottom face. First apply the Pythagorean Theorem to find the length of the diagonal of the bottom face, and then apply the Pythagorean Theorem again with this side and the height of the prism to find the length of its diagonal:

\displaystyle L^2+W^2=C^2

\displaystyle 6^2+4^2=C^2

\displaystyle C^2=52\rightarrow C=\sqrt{52}

\displaystyle H^2+C^2=D^2

\displaystyle 3^2+(\sqrt{52})^2=D^2

\displaystyle D^2=61\rightarrow D=\sqrt{61}

Example Question #791 : Gmat Quantitative Reasoning

Calculate the diagonal length for a rectangular prism with a length of  \displaystyle 8,  a width of  \displaystyle 5,  and a height of  \displaystyle 3.

Possible Answers:

\displaystyle 7\sqrt{2}

\displaystyle 4\sqrt{3}

\displaystyle 2\sqrt{5}

\displaystyle 10\sqrt{6}

Correct answer:

\displaystyle 7\sqrt{2}

Explanation:

The diagonal of a rectangular prism can be thought of as the hypotenuse of a right triangle, where the other two sides are the height of the prism and the diagonal of either its top or bottom face. This means we can find the length of the prism's diagonal using the Pythagorean Theorem, but first we must apply this theorem to find the diagonal of the prism's top or bottom face, which forms the base of the right triangle whose hypotenuse is the diagonal of the entire prism. After finding the face diagonal, we apply the Pythagorean Theorem again to calculate the answer:

\displaystyle a^2+b^2=c^2

\displaystyle 8^2+5^2=c^2

\displaystyle c^2=89\rightarrow c=\sqrt{89}

\displaystyle h^2+c^2=d^2

\displaystyle 3^2+(\sqrt{89})^2=d^2

\displaystyle d^2=98\rightarrow d=\sqrt{98}=\sqrt{2\cdot 49}=7\sqrt{2}

Example Question #3 : Calculating The Diagonal Of A Prism

Calculate the diagonal length for a rectangular prism with a length of  \displaystyle 4,  a width of  \displaystyle 3,  and a height of  \displaystyle 2.

Possible Answers:

\displaystyle \sqrt{17}

\displaystyle 8\sqrt{3}

\displaystyle \sqrt{29}

\displaystyle \sqrt{22}

Correct answer:

\displaystyle \sqrt{29}

Explanation:

The diagonal of a rectangular prism can be thought of as the hypotenuse of a right triangle whose other two sides are the height of the prism and the diagonal of either its top or bottom face. We start by finding the diagonal of either the prism's top or bottom face, as this is the base of the right triangle for which the diagonal of the prism is the hypotenuse:

\displaystyle a^2+b^2=c^2

\displaystyle 4^2+3^2=c^2

\displaystyle c^2=25\rightarrow c=5

Now we apply the Pythagorean Theorem again, this time using the prism height and the face diagonal calculated above, and the hypotenuse we're left with is the same as the diagonal length of the rectangular prism:

\displaystyle h^2+c^2=d^2

\displaystyle 2^2+5^2=d^2

\displaystyle c^2=29\rightarrow c=\sqrt{29}

Example Question #4 : Calculating The Diagonal Of A Prism

A rectangular prism has a height of \displaystyle 9, a length of \displaystyle 12, and a width \displaystyle 4. What is the length of the prism's diagonal?

Possible Answers:

\displaystyle \sqrt{241}

\displaystyle 4\sqrt{10}

\displaystyle \sqrt{140}

\displaystyle 6\sqrt{10}

\displaystyle 8\sqrt{10}

Correct answer:

\displaystyle \sqrt{241}

Explanation:

The diagonal of a rectangular prism is the hypotenuse of the right triangle formed by the height of the prism and the diagonal of its bottom face. Thus, we apply the Pythagorean Theorem twice: first to find the bottom face's diagonal, and again to find the diagonal of the prism. For the bottom face's diagonal \displaystyle c, use the Pythagorean Theorem with the given length and width:

\displaystyle l^{2} +w^{2}=c^{2}

\displaystyle \sqrt{l^{2} +w^{2}}=c^{2}

\displaystyle \sqrt{12^{2} +4^{2}}=c

\displaystyle \sqrt{144 +16}=c

\displaystyle \sqrt{160}=c

\displaystyle \sqrt{16\times 10}=c

\displaystyle 4\sqrt{10}=c

Using this value \displaystyle c, we can now find the value of the prism's diagonal \displaystyle d:

\displaystyle h^{2}+c^{2}=d^{2}

\displaystyle \sqrt{h^{2} +c^{2}}=d

\displaystyle \sqrt{9^{2} +(\sqrt{160})^{2}}=d

\displaystyle \sqrt{81 +160}=d

\displaystyle \sqrt{241}=d

Example Question #5 : Calculating The Diagonal Of A Prism

A rectangular prism has a height of \displaystyle 6, a length of \displaystyle 8, and a width \displaystyle 10. What is the length of the prism's diagonal?

Possible Answers:

None of the above.

\displaystyle 2\sqrt{41}

\displaystyle 4\sqrt{41}

\displaystyle 10\sqrt{2}

\displaystyle 20\sqrt{2}

Correct answer:

\displaystyle 10\sqrt{2}

Explanation:

The diagonal of a rectangular prism is the hypotenuse of the right triangle formed by the height of the prism and the diagonal of its bottom face. Thus, we apply the Pythagorean Theorem twice: first to find the bottom face's diagonal, and again to find the diagonal of the prism. For the bottom face's diagonal \displaystyle c, use the Pythagorean Theorem with the given length and width:

\displaystyle l^{2} +w^{2}=c^{2}

\displaystyle \sqrt{l^{2} +w^{2}}=c^{2}

\displaystyle \sqrt{8^{2} +10^{2}}=c

\displaystyle \sqrt{64 +100}=c

\displaystyle \sqrt{164}=c

\displaystyle \sqrt{41\times 4}=c

\displaystyle 2\sqrt{41}=c

Using this value \displaystyle c, we can now find the value of the prism's diagonal \displaystyle d:

\displaystyle h^{2}+c^{2}=d^{2}

\displaystyle \sqrt{h^{2} +c^{2}}=d

\displaystyle \sqrt{6^{2} +(\sqrt{164})^{2}}=d

\displaystyle \sqrt{36 +164}=d

\displaystyle \sqrt{200}=d

\displaystyle \sqrt{100\times 2}=d

\displaystyle 10\sqrt{2}=d

 

Example Question #3 : Calculating The Diagonal Of A Prism

A rectangular prism has a height of \displaystyle 11, a length of \displaystyle 7, and a width \displaystyle 4. What is the length of the prism's diagonal?

Possible Answers:

\displaystyle 16

\displaystyle 8

\displaystyle 4

\displaystyle \sqrt{186}

\displaystyle 2\sqrt{185}

Correct answer:

\displaystyle \sqrt{186}

Explanation:

The diagonal of a rectangular prism is the hypotenuse of the right triangle formed by the height of the prism and the diagonal of its bottom face. Thus, we apply the Pythagorean Theorem twice: first to find the bottom face's diagonal, and again to find the diagonal of the prism. For the bottom face's diagonal \displaystyle c, use the Pythagorean Theorem with the given length and width:

\displaystyle l^{2} +w^{2}=c^{2}

\displaystyle \sqrt{l^{2} +w^{2}}=c^{2}

\displaystyle \sqrt{7^{2} +4^{2}}=c

\displaystyle \sqrt{49 +16}=c

\displaystyle \sqrt{65}=c

 

Using this value \displaystyle c, we can now find the value of the prism's diagonal \displaystyle d:

\displaystyle h^{2}+c^{2}=d^{2}

\displaystyle \sqrt{h^{2} +c^{2}}=d

\displaystyle \sqrt{11^{2} +\sqrt{65}^{2}}=d

\displaystyle \sqrt{121+65}=d

\displaystyle \sqrt{186}=d

 

 

 

Tired of practice problems?

Try live online GMAT prep today.

1-on-1 Tutoring
Live Online Class
1-on-1 + Class
Learning Tools by Varsity Tutors