Advanced Geometry : Tetrahedrons

Study concepts, example questions & explanations for Advanced Geometry

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Example Questions

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

Find the volume of a tetrahedron with an edge of \(\displaystyle 6\sqrt2\).

Possible Answers:

\(\displaystyle 72\)

\(\displaystyle 36\)

\(\displaystyle 96\)

\(\displaystyle 48\)

\(\displaystyle 24\)

Correct answer:

\(\displaystyle 72\)

Explanation:

Write the formula the volume of a tetrahedron.

\(\displaystyle V=\frac{s^3}{6\sqrt 2}\)

Substitute the edge length provided in the equation into the formula.

\(\displaystyle V= \frac{(6\sqrt 2)^3}{6\sqrt 2}\)

Cancel out the denominator with part of the numerator and solve the remaining part of the numerator to arrive at the correct answer.

\(\displaystyle V= (6\sqrt 2)^2 = 72\)

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

Find the volume of a tetrahedron with an edge of \(\displaystyle \sqrt5\).

Possible Answers:

\(\displaystyle \frac{25\sqrt10}{12}\)

\(\displaystyle 5\sqrt3\)

\(\displaystyle \frac{125}{6}\)

\(\displaystyle \frac{125\sqrt2}{12}\)

\(\displaystyle \frac{5\sqrt3}{9}\)

Correct answer:

\(\displaystyle \frac{25\sqrt10}{12}\)

Explanation:

Write the formula the volume of a tetrahedron and substitute in the provided edge length.

\(\displaystyle V=\frac{s^3}{6\sqrt 2}= \frac{(\sqrt 5)^3}{6\sqrt 2} = \frac{25\sqrt 5}{6\sqrt2}\)

Rationalize the denominator to arrive at the correct answer.

\(\displaystyle \frac{25\sqrt5}{6\sqrt2} \cdot \frac{\sqrt2}{\sqrt2} = \frac{25\sqrt 10}{12}\)

 

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

Find the volume of the regular tetrahedron with side length \(\displaystyle 5\:cm\).

Possible Answers:

\(\displaystyle 125.00\:cm^3\)

\(\displaystyle 14.73\:cm^3\)

\(\displaystyle 20.83\:cm^3\)

\(\displaystyle 12.03\:cm^3\)

\(\displaystyle 2.95\:cm^3\)

Correct answer:

\(\displaystyle 14.73\:cm^3\)

Explanation:

The formula for the volume of a regular tetrahedron is:

\(\displaystyle V = \frac{s^3}{6\sqrt{2}}\)

Where \(\displaystyle s\) is the length of side. Using this formula and the given values, we get:

\(\displaystyle V = \frac{5\:cm^3}{6\sqrt{2}} = 14.73\:cm^3\)

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

What is the volume of a regular tetrahedron with edges of \(\displaystyle 6cm\)?

Possible Answers:

\(\displaystyle \small \frac{36}{\sqrt{2}} cm^3\)

\(\displaystyle \small \sqrt{2} cm^3\)

\(\displaystyle \small 6\sqrt{2} cm^3\)

\(\displaystyle \small \frac{36}{\sqrt{2}} cm^3\)

\(\displaystyle \small \frac{216}{\sqrt{2}} cm^3\)

Correct answer:

\(\displaystyle \small \frac{36}{\sqrt{2}} cm^3\)

Explanation:

The volume of a tetrahedron is found with the formula:

 \(\displaystyle \small V= \frac{a^3}{6\sqrt{2}}\) ,

where \(\displaystyle \small a\) is the length of the edges.

When \(\displaystyle \small a=6\)

\(\displaystyle \small V=\frac{36}{\sqrt{2}}\).

Example Question #91 : Geometry

What is the volume of a regular tetrahedron with edges of \(\displaystyle \small \frac{2}{3} cm\)?

Possible Answers:

\(\displaystyle \small \frac{4}{81\sqrt{2}} cm^3\)

\(\displaystyle \small \frac{4}{81\sqrt{2}} cm^2\)

None of the above.

\(\displaystyle \small \frac{2}{9\sqrt{2}}cm^2\)

\(\displaystyle \small \frac{2}{9\sqrt{2}}cm^3\)

Correct answer:

\(\displaystyle \small \frac{4}{81\sqrt{2}} cm^3\)

Explanation:

The volume of a tetrahedron is found with the formula,

 \(\displaystyle \small V= \frac{a^3}{6\sqrt{2}}\) where \(\displaystyle \small a\) is the length of the edges.

When \(\displaystyle \small a= \frac{2}{3}\) the volume becomes,

\(\displaystyle \small V= \left ( \frac{2}{3} ^3\right )\div 6\sqrt{2}\)

\(\displaystyle \small V=\frac{8}{27}\div 6\sqrt{2}\)

\(\displaystyle \small V= \frac{8}{27}\times\frac{1}{6\sqrt{2}}=\frac{4}{81\sqrt{2}}\)

The answer is in volume, so it must be in a cubic measurement!

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

What is the volume of a regular tetrahedron with edges of \(\displaystyle \small \small \frac{4}{5}cm\)?

Possible Answers:

\(\displaystyle \small \frac{32}{\sqrt{2}}\) \(\displaystyle \small cm^3\)

None of the above.

\(\displaystyle \small \frac{375}{32\sqrt{2}}\)

\(\displaystyle \small 375\sqrt{2}\)

\(\displaystyle \small \frac{125}{\sqrt{2}}\) \(\displaystyle \small cm^3\)

Correct answer:

None of the above.

Explanation:

The volume of a tetrahedron is found with the formula \(\displaystyle \small V= \frac{a^3}{6\sqrt{2}}\) where \(\displaystyle \small a\) is the length of the edges.

When \(\displaystyle \small \small a= \frac{4}{5}\)

\(\displaystyle \small \small V= \left ( \frac{4}{5} ^3\right )\div 6\sqrt{2}\)

\(\displaystyle \small \small V=\frac{64}{125}\div 6\sqrt{2}\)

\(\displaystyle \small \small \small V= \frac{64}{125}\times\frac{1}{6\sqrt{2}}=\frac{64}{750\sqrt{2}}=\frac{32}{375\sqrt{2}}\)

 

This answer is not found, so it is "none of the above."

Example Question #11 : Volume

How is the volume of a regular tetrahedron effected when the length of each edge is doubled?

Possible Answers:

It is 4 times greater.

It is doubled.

It increases by 50%.

It cannot be determined by the information given.

It is 8 times greater.

Correct answer:

It is 8 times greater.

Explanation:

The volume of a regular tetrahedron is found with the formula \(\displaystyle \small \small V_{1}= \frac{a^3}{6\sqrt{2}}\) where \(\displaystyle \small a\) is the length of the edges. 

The volume of the same tetrahedron when the length of the edges are doubled would be \(\displaystyle \small \small \small V_{2}= \frac{(2a)^3}{6\sqrt{2}}\).

Therefore,

\(\displaystyle \small V_{2}=\frac{8a^3}{6\sqrt{2}}=8\times V_{1}\)

 

Example Question #81 : Solid Geometry

What is the volume of a regular tetrahedron with edges of \(\displaystyle \small 22\) \(\displaystyle \small cm\)?

Possible Answers:

\(\displaystyle \small \frac{5324}{3\sqrt{2}}\) \(\displaystyle \small cm^2\)

\(\displaystyle \small \frac{2662}{3\sqrt{2}}\) \(\displaystyle \small cm^3\)

\(\displaystyle \small \frac{2662}{3\sqrt{2}}\) \(\displaystyle \small cm^2\)

None of the above.

\(\displaystyle \small \frac{5324}{3\sqrt{2}}\) \(\displaystyle \small cm^3\)

Correct answer:

\(\displaystyle \small \frac{5324}{3\sqrt{2}}\) \(\displaystyle \small cm^3\)

Explanation:

The volume of a tetrahedron is found with the formula \(\displaystyle \small V= \frac{a^3}{6\sqrt{2}}\) where \(\displaystyle \small a\) is the length of the edges.

When \(\displaystyle \small \small a= 22\),

 \(\displaystyle \small \small \small V=\frac{22^3}{6\sqrt{2}}\)

\(\displaystyle \small V=\frac{10648}{6\sqrt{2}}=\frac{5324}{3\sqrt{2}}\)

And, of course, volume should be in cubic measurements!

Example Question #42 : Tetrahedrons

Find the volume of a regular tetrahedron if one of its edges is \(\displaystyle \sqrt[3]{6}\:cm\) long.

Possible Answers:

\(\displaystyle 2\sqrt6\:cm\)

\(\displaystyle 4\sqrt3\:cm\)

\(\displaystyle 2\sqrt3\:cm\)

\(\displaystyle \frac{\sqrt2}{2}\;cm\)

\(\displaystyle \sqrt6\:cm\)

Correct answer:

\(\displaystyle \frac{\sqrt2}{2}\;cm\)

Explanation:

Write the volume equation for a tetrahedron.

\(\displaystyle V=\frac{e^3}{6\sqrt2}\)

In this formula, \(\displaystyle V\) stands for the tetrahedron's volume and \(\displaystyle e\) stands for the length of one of its edges.

Substitute the given edge length and solve.

\(\displaystyle V=\frac{(\sqrt[3]6\:cm)^3}{6\sqrt2} = \frac{6\:cm^3}{6\sqrt2}= \frac{1}{\sqrt2}\:cm\)

Rationalize the denominator.

\(\displaystyle \frac{1}{\sqrt2}\:cm\cdot \frac{\sqrt2}{\sqrt2} = \frac{\sqrt2}{2}\:cm\)

Example Question #11 : How To Find The Volume Of A Tetrahedron

Find the volume of a tetrahedron if the side length is \(\displaystyle \frac{1}{6}\).

Possible Answers:

\(\displaystyle \frac{\sqrt2}{16}\)

\(\displaystyle \frac{3\sqrt2}{2}\)

\(\displaystyle \frac{\sqrt2}{2592}\)

\(\displaystyle \frac{\sqrt2}{216}\)

\(\displaystyle \frac{\sqrt2}{1296}\)

Correct answer:

\(\displaystyle \frac{\sqrt2}{2592}\)

Explanation:

Write the equation to find the volume of a tetrahedron.

\(\displaystyle V=\frac{a^3}{6\sqrt2}\)

Substitute the side length and solve for the volume.

\(\displaystyle V=\frac{(\frac{1}{6})^3}{6\sqrt2}= \frac{1}{216}\left(\frac{1}{6\sqrt2}\right)= \frac{1}{1296\sqrt2}\)

Rationalize the denominator.

\(\displaystyle V=\frac{1}{1296\sqrt2} \cdot \frac{\sqrt2}{\sqrt2}= \frac{\sqrt2}{1296\cdot 2} = \frac{\sqrt2}{2592}\)

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