Advanced Geometry : How to find the surface area of a tetrahedron

Study concepts, example questions & explanations for Advanced Geometry

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Example Questions

Example Question #11 : Tetrahedrons

What is the surface area of the following tetrahedron? Assume the figure is a regular tetrahedron.

Tetrahedron

Possible Answers:

\(\displaystyle 2\sqrt{3}m^2\)

\(\displaystyle \frac{\sqrt{3}}{2}m^2\)

\(\displaystyle 4\sqrt{3}m^2\)

\(\displaystyle 3\sqrt{3}m^2\)

\(\displaystyle 8\sqrt{3}m^2\)

Correct answer:

\(\displaystyle 4\sqrt{3}m^2\)

Explanation:

A tetrahedron is a three-dimensonal figure where each side is an equilateral triangle. Therefore, each angle in the triangle is \(\displaystyle 60^{\circ}\).

In the figure, we know the value of the side \(\displaystyle (2\: m)\) and the value of the base \(\displaystyle (1\: m)\). Since dividing the triangle by half creates a \(\displaystyle 30^{\circ}-60^{\circ}-90^{\circ}\) triangle, we know the value of \(\displaystyle h\) must be \(\displaystyle \sqrt{3}\: m\).

Therefore, the area of one side of the tetrahedron is:

\(\displaystyle A = (b)(h) = (1\: m)(\sqrt{3}\: m) = \sqrt{3}\: m^2\)

Since there are four sides of a tetrahedron, the surface area is:

\(\displaystyle SA = 4 (b)(h) = 4\sqrt{3}\: m^2\)

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

A regular tetrahedron has side lengths \(\displaystyle s=1\). What is the surface area of the described solid?

Possible Answers:

\(\displaystyle 2\sqrt3\)

\(\displaystyle 4\sqrt{3}\)

\(\displaystyle 2\)

\(\displaystyle \sqrt{3}\)

Correct answer:

\(\displaystyle \sqrt{3}\)

Explanation:

The area of one face of the triangle can be found either through trigonometry or the Pythagorean Theorem.

Since all the sides of the triangle are \(\displaystyle 1\), the height is then\(\displaystyle \frac{\sqrt{3}}{2}\), so the area of each face is:

\(\displaystyle \frac{bh}{2}=\frac{1}{2} \cdot 1 \cdot \frac{\sqrt{3}}{2}=\frac{\sqrt{3}}{4}\)

There are four faces, so the area of the tetrahedron is:

 \(\displaystyle 4 \cdot \frac{bh}{2}=\sqrt3\)

Example Question #3 : How To Find The Surface Area Of A Tetrahedron

Find the surface area of a regular tetrahedron with a side length of \(\displaystyle 4\).

Possible Answers:

\(\displaystyle 2\sqrt3\)

\(\displaystyle 16\sqrt3\)

\(\displaystyle 8\sqrt3\)

\(\displaystyle 4\sqrt3\)

Correct answer:

\(\displaystyle 16\sqrt3\)

Explanation:

Use the following formula to find the surface area of a regular tetrahedron.

\(\displaystyle \text{Surface Area}=\sqrt3 (side^2)\)

Now, substitute in the value of the side length into the equation.

\(\displaystyle \text{Surface Area}=\sqrt3(4^2)=16\sqrt3\)

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

Find the surface area of a regular tetrahedron with a side length of \(\displaystyle 12\).

Possible Answers:

\(\displaystyle 144\sqrt3\)

\(\displaystyle 96\sqrt3\)

\(\displaystyle 12\sqrt3\)

\(\displaystyle 36\sqrt3\)

Correct answer:

\(\displaystyle 144\sqrt3\)

Explanation:

Use the following formula to find the surface area of a regular tetrahedron.

\(\displaystyle \text{Surface Area}=\sqrt3 (side^2)\)

Now, substitute in the value of the side length into the equation.

\(\displaystyle \text{Surface Area}=\sqrt3(12^2)=144\sqrt3\)

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

In terms of \(\displaystyle x\), find the surface area of a regular tetrahedron that has a side length of \(\displaystyle 5x\).

Possible Answers:

\(\displaystyle 25x\sqrt3\)

\(\displaystyle 125x^2\sqrt3\)

\(\displaystyle 5x^2\sqrt3\)

\(\displaystyle 25x^2\sqrt3\)

Correct answer:

\(\displaystyle 25x^2\sqrt3\)

Explanation:

Use the following formula to find the surface area of a regular tetrahedron.

\(\displaystyle \text{Surface Area}=\sqrt3 (side^2)\)

Now, substitute in the value of the side length into the equation.

\(\displaystyle \text{Surface Area}=\sqrt3(5x)^2=25x^2\sqrt3\)

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

In terms of \(\displaystyle q\), find the surface area of a regular tetrahedron with side lengths of \(\displaystyle 3q\).

Possible Answers:

\(\displaystyle 27q^2\sqrt3\)

\(\displaystyle 9q\sqrt3\)

\(\displaystyle 9q^2\sqrt3\)

\(\displaystyle 3q\sqrt3\)

Correct answer:

\(\displaystyle 9q^2\sqrt3\)

Explanation:

Use the following formula to find the surface area of a regular tetrahedron.

\(\displaystyle \text{Surface Area}=\sqrt3 (side^2)\)

Now, substitute in the value of the side length into the equation.

\(\displaystyle \text{Surface Area}=\sqrt3(3q)^2=9q^2\sqrt3\)

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

The surface area of a regular tetrahedron is \(\displaystyle 36\sqrt3\). If the length of each side is \(\displaystyle 3a\), find the value of \(\displaystyle a\).

Possible Answers:

\(\displaystyle 2\)

\(\displaystyle 6\)

\(\displaystyle 4\)

\(\displaystyle 5\)

Correct answer:

\(\displaystyle 2\)

Explanation:

Use the following formula to find the surface area of a regular tetrahedron.

\(\displaystyle \text{Surface Area}=\sqrt3 (side^2)\)

Now, substitute in the value of the side length into the equation.

\(\displaystyle 36\sqrt3=\sqrt3(3a)^2\)

Now, solve for \(\displaystyle a\).

\(\displaystyle 9a^2=36\)

\(\displaystyle a^2=4\)

\(\displaystyle a=2\)

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

The surface area of a regular tetrahedron is \(\displaystyle 54\). If each side length is \(\displaystyle 6x\), find the value of \(\displaystyle x\). Round to the nearest tenths place.

Possible Answers:

\(\displaystyle 2.4\)

\(\displaystyle 8.4\)

\(\displaystyle 0.9\)

\(\displaystyle 1.7\)

Correct answer:

\(\displaystyle 0.9\)

Explanation:

Use the following formula to find the surface area of a regular tetrahedron.

\(\displaystyle \text{Surface Area}=\sqrt3 (side^2)\)

Now, substitute in the value of the side length into the equation.

\(\displaystyle 54=\sqrt3(6x)^2\)

Solve for \(\displaystyle x\).

\(\displaystyle 36x^2\sqrt3=54\)

\(\displaystyle x^2\sqrt3=1.5\)

\(\displaystyle x^2=\frac{1.5}{\sqrt3}=0.866\)

\(\displaystyle x=\sqrt{0.866}=0.9\)

Example Question #9 : How To Find The Surface Area Of A Tetrahedron

The surface area of a regular tetrahedron is \(\displaystyle 64\). If each side length is \(\displaystyle 4x\), find the value of \(\displaystyle x\). Round to the nearest tenths place.

Possible Answers:

\(\displaystyle 0.7\)

\(\displaystyle 2.3\)

\(\displaystyle 1.5\)

\(\displaystyle 1.9\)

Correct answer:

\(\displaystyle 1.5\)

Explanation:

Use the following formula to find the surface area of a regular tetrahedron.

\(\displaystyle \text{Surface Area}=\sqrt3 (side^2)\)

Now, substitute in the value of the side length into the equation.

\(\displaystyle 64=\sqrt3(4x)^2\)

\(\displaystyle 16x^2=\frac{64}{\sqrt3}\)

\(\displaystyle x^2=\frac{64}{16\sqrt3}=2.309\)

\(\displaystyle x=1.5\)

 

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

The surface area of a regular tetrahedron is \(\displaystyle 100\sqrt3\). If each side length is \(\displaystyle x-1\), find the value of \(\displaystyle x\).

Possible Answers:

\(\displaystyle 12\)

\(\displaystyle 11\)

\(\displaystyle 10\)

\(\displaystyle 9\)

Correct answer:

\(\displaystyle 11\)

Explanation:

Use the following formula to find the surface area of a regular tetrahedron.

\(\displaystyle \text{Surface Area}=\sqrt3 (side^2)\)

Now, substitute in the value of the side length into the equation and solve for \(\displaystyle x\).

\(\displaystyle 100\sqrt3=\sqrt3(x-1)^2\)

\(\displaystyle (x-1)^2=100\)

\(\displaystyle x^2-2x+1=100\)

\(\displaystyle x^2-2x-99=0\)

\(\displaystyle (x-11)(x+9)=0\)

\(\displaystyle x=11, x=-9\)

Since we are dealing with a 3-dimensional shape, only \(\displaystyle x=11\) is valid.

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