SSAT Upper Level Math : Equilateral Triangles

Study concepts, example questions & explanations for SSAT Upper Level Math

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Example Questions

Example Question #1 : Equilateral Triangles

An equilateral triangle has a perimeter of \displaystyle 2400 units. What is the length of each side?

Possible Answers:

\displaystyle 800 units

\displaystyle 400 units

\displaystyle 300 units

\displaystyle 600 units

Correct answer:

\displaystyle 800 units

Explanation:

Because an equilateral triangle has three sides that are the same length, divide the given perimeter by 3 to find the length of each side.

\displaystyle 2400\div3=800

Example Question #1 : How To Find The Length Of The Side Of An Equilateral Triangle

The perimeter of a equilateral triangle is \displaystyle 99\:m. In meters, what is the length of a side of this triangle?

Possible Answers:

\displaystyle 33\:m

\displaystyle 56\:m

\displaystyle 49.5\:m

\displaystyle 66\:m

Correct answer:

\displaystyle 33\:m

Explanation:

Since all three sides are equal in an equilateral triangle, we can just divide the perimeter by 3 to find a side length.

\displaystyle 99\:m\div3\:m=33\:m

Example Question #2 : How To Find The Length Of The Side Of An Equilateral Triangle

The perimeter of an equilateral triangle is \displaystyle 36x. What is the length of a side of this triangle?

Possible Answers:

\displaystyle 12x

\displaystyle 24x

\displaystyle 12

\displaystyle 24

Correct answer:

\displaystyle 12x

Explanation:

Because all the sides in an equilateral triangle are equal, we can just divide the perimeter by 3 to find the length of a side.

\displaystyle 36x\div3=12x

Example Question #3 : How To Find The Length Of The Side Of An Equilateral Triangle

The perimeter of an equilateral triangle is \displaystyle 120t. What is the length of one side of the triangle?

Possible Answers:

\displaystyle 20t

\displaystyle 40t

\displaystyle 30t

\displaystyle 40

Correct answer:

\displaystyle 40t

Explanation:

Since an equilateral triangle has sides that are all the same, divide the perimeter by \displaystyle 3 to get the length of each side.

\displaystyle 120t\div3=40t

Example Question #2 : Equilateral Triangles

The perimeter of an equilateral triangle is 39 meters. In meters, how long is one side of the triangle?

Possible Answers:

\displaystyle 26

\displaystyle 17

\displaystyle 8

\displaystyle 13

Correct answer:

\displaystyle 13

Explanation:

An equilateral triangle has sides that are the same length. Then, to find the length of one side, you only need to divide the perimeter by 3.

\displaystyle 39\div3=13

Example Question #3 : Equilateral Triangles

The perimeter of an equilateral triangle is \displaystyle 75c+12. What is the length of one side of this triangle?

Possible Answers:

\displaystyle 75c+4

\displaystyle 25c+12

\displaystyle 79

\displaystyle 25c+4

Correct answer:

\displaystyle 25c+4

Explanation:

Since an equilateral triangle has three equal sides, divide the perimeter by \displaystyle 3 to find the length of each side.

\displaystyle \frac{75c+12}{3}=25c+4

Example Question #4 : How To Find The Length Of The Side Of An Equilateral Triangle

The perimeter of an equilateral triangle is \displaystyle 24d-18. What is the length of one side of this triangle?

Possible Answers:

\displaystyle 8d+6

\displaystyle 2

\displaystyle 8d-6

\displaystyle d+6

Correct answer:

\displaystyle 8d-6

Explanation:

Since an equilateral triangle has three equal sides, divide the perimeter by \displaystyle 3 to find the length of one side.

\displaystyle \frac{24d-18}{3}=8d-6

Example Question #52 : Geometry

What is the difference between an equilateral triangle and a scalene triangle? 

Possible Answers:

The number of side lengths 

The length of their sides

The sum of their angle measurements

Their color 

The sum of their side lengths 

Correct answer:

The length of their sides

Explanation:

Of the choices listed, the main difference between an equilateral triangle and a scalene triangle is their side lengths. An equilateral triangle has to have \displaystyle 3 equal sides, but a scalene triangle can have all different side lengths. 

Example Question #1 : Equilateral Triangles

An equilateral triangle is circumscribed about a circle of radius 16. Give the area of the triangle.

Possible Answers:

\displaystyle 3,072\sqrt{2}

\displaystyle 768 \sqrt{2}

The correct answer is not among the other choices.

\displaystyle 768 \sqrt{3}

\displaystyle 3,072\sqrt{3}

Correct answer:

\displaystyle 768 \sqrt{3}

Explanation:

The circle and triangle referenced are below, along with a radius to one side and a segment to one vertex:

Equilateral

\displaystyle \Delta ABO is a 30-60-90 triangle, so 

\displaystyle AB = OB \cdot \sqrt{3} = 16 \sqrt{3}

\displaystyle \overline{AB} is one-half of a side of the triangle, so the sidelength is \displaystyle 32\sqrt{3}. The area of the triangle is

\displaystyle A = \frac{s^{2} \sqrt{3}}{4} = \frac{(32\sqrt{3})^{2} \sqrt{3}}{4} = \frac{1,024 \cdot 3 \cdot \sqrt{3}}{4}= 768 \sqrt{3}

Example Question #1 : How To Find The Area Of An Equilateral Triangle

Equilateral

In the above diagram, \displaystyle \Delta ABC is equilateral. Give its area.

Possible Answers:

\displaystyle 1,024

\displaystyle 512 \sqrt{3}

The correct answer is not among the other responses.

\displaystyle 512 \sqrt{6}

\displaystyle 512 \sqrt{2}

Correct answer:

The correct answer is not among the other responses.

Explanation:

The interior angles of an equilateral triangle all measure 60 degrees, so, by the 30-60-90 Theorem, 

\displaystyle BM = \frac{AM}{\sqrt{3}} = \frac{32}{\sqrt{3}}

Also, \displaystyle M is the midpoint of \displaystyle \overline{BC}, so \displaystyle BC = 2 \cdot BM = \frac{64}{\sqrt{3}}; this is the base.

The area of this triangle is half the product of the base \displaystyle BC and the height \displaystyle AM:

\displaystyle A= \frac{1}{2} \cdot 32 \cdot \frac{64}{\sqrt{3}}= \frac{1,024}{\sqrt{3}} = \frac{1,024\cdot \sqrt{3}}{\sqrt{3} \cdot \sqrt{3}}= \frac{1,024 \sqrt{3}}{3}

This answer is not among the given choices.

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