GED Math : Triangles

Study concepts, example questions & explanations for GED Math

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Example Questions

Example Question #1 : Triangles

If \(\displaystyle \Delta MNO \cong \Delta PQR\), then which segment is congruent to \(\displaystyle \overline{NO}\) ?

Possible Answers:

\(\displaystyle \overline{MO}\)

\(\displaystyle \overline{NQ}\)

\(\displaystyle \overline{RP}\)

\(\displaystyle \overline{RQ}\)

Correct answer:

\(\displaystyle \overline{RQ}\)

Explanation:

A congruency statement about two triangles implies nothing about the relationship between two sides of the same triangle, so we can eliminate \(\displaystyle \overline{MO}\). Also, the length of a segment with endpoints on two different  triangles depends on their positioning, not their congruence, so we can eliminate \(\displaystyle \overline{NQ}\).

Since \(\displaystyle N\) and \(\displaystyle O\) are in the same positions in the name of the first triangle as \(\displaystyle Q\) and \(\displaystyle R\)\(\displaystyle \overline{NO}\) and \(\displaystyle \overline{QR}\) are corresponding sides of congruent triangles, and 

\(\displaystyle \overline{NO} \cong \overline{QR}\)

Since the letters of the name of a segment are interchangeable, this statement can be rewritten as

\(\displaystyle \overline{NO} \cong \overline{RQ}\),

making \(\displaystyle \overline{RQ}\) the correct choice.

Example Question #2 : Triangles

A triangle has sides of length 36 inches, 3 feet, and one yard. Choose the statement that most accurately describes this triangle.

Possible Answers:

This triangle is isosceles but not equilateral.

This triangle is scalene.

This triangle is equilateral.

More information is needed to answer this question.

Correct answer:

This triangle is equilateral.

Explanation:

One yard is equal to three feet, or thirty-six inches. The three given sidelengths are equal to one another, making this an equilateral triangle.

Example Question #2 : Triangles

Right_triangle

Note: Figure NOT drawn to scale.

Refer to the above diagram. Evaluate \(\displaystyle X\).

Possible Answers:

\(\displaystyle X= 10 \frac{1}{12}\)

\(\displaystyle X = 11\frac{1}{13}\)

\(\displaystyle x = 10 \frac{12}{13}\)

\(\displaystyle x = 10\)

Correct answer:

\(\displaystyle X = 11\frac{1}{13}\)

Explanation:

The altitude perpendicular to the hypotenuse of a right triangle divides that triangle into two smaller triangles similar to each other and the large triangle. Therefore, the sides are in proportion. The hypotenuse of the triangle is equal to

\(\displaystyle \sqrt{5^{2}+12^{2}} = \sqrt{25+144} = \sqrt{169} =13\).

Therefore, we can set up a proportion and solve for \(\displaystyle X\):

\(\displaystyle \frac{X}{12} = \frac{12}{13}\)

\(\displaystyle \frac{X}{12}\cdot 12 = \frac{12}{13} \cdot 12\)

\(\displaystyle X = \frac{144}{13} = 11\frac{1}{13}\)

Example Question #2 : Perimeter And Sides Of Triangles

If the base of an equilateral triangle is 16cm, find the perimeter.

Possible Answers:

\(\displaystyle 56\text{cm}\)

\(\displaystyle 48\text{cm}\)

\(\displaystyle 64\text{cm}\)

\(\displaystyle \text{There is not enough information to solve the problem.}\)

\(\displaystyle 32\text{cm}\)

Correct answer:

\(\displaystyle 48\text{cm}\)

Explanation:

To find the perimeter of a triangle, we will use the following formula:

\(\displaystyle P = a+b+c\)

where a, b, and c are the lengths of the sides of the triangle.

 

Now, we know the base of the triangle is 16cm. Because it is an equilateral triangle, all sides are equal. Therefore, all sides are 16cm.  So, we get

\(\displaystyle P = 16\text{cm} +16\text{cm} +16\text{cm}\)

\(\displaystyle P = 48\text{cm}\)

Example Question #1 : Triangles

The perimeter of an equilateral triangle is 36in.  Find the length of one side.

Possible Answers:

\(\displaystyle 12\text{in}\)

\(\displaystyle 14\text{in}\)

\(\displaystyle 11\text{in}\)

\(\displaystyle 13\text{in}\)

\(\displaystyle 9\text{in}\)

Correct answer:

\(\displaystyle 12\text{in}\)

Explanation:

The formula to find the perimeter of an equilateral triangle is

\(\displaystyle P = 3a\)

where a is the length of one side of the triangle. Because it is an equilateral triangle, all sides are equal. Therefore, we can use any side in the formula. To find the length of one side, we will solve for a.

Now, we know the perimeter of the equilateral triangle is 36in. So, we will substitute and solve for a. We get

\(\displaystyle 36\text{in} = 3a\)

 

\(\displaystyle \frac{36\text{in}}{3} = \frac{3a}{3}\)

 

\(\displaystyle 12\text{in} = a\)

 

\(\displaystyle a = 12\text{in}\)

 

Therefore, the length of one side of the equilateral triangle is 12in.

Example Question #3 : Triangles

Find the perimeter of an equilateral triangle with a side having a length of 17in.

Possible Answers:

\(\displaystyle 34\text{in}\)

\(\displaystyle 51\text{in}\)

\(\displaystyle 28\text{in}\)

\(\displaystyle 42\text{in}\)

\(\displaystyle 48\text{in}\)

Correct answer:

\(\displaystyle 51\text{in}\)

Explanation:

To find the perimeter of a triangle, we will use the following formula:

\(\displaystyle P = a+b+c\)

where a, b, and c are the lengths of the sides of the triangle.

Now, we know one side of the triangle has a length of 17in. Because it is an equilateral triangle, all sides are equal. Therefore, all sides are 17in. So, we can substitute. We get

\(\displaystyle P = 17\text{in} +17\text{in} +17\text{in}\)

\(\displaystyle P = 51\text{in}\)

Example Question #1 : Perimeter And Sides Of Triangles

An equilateral triangle has a perimeter of 69in.  Find the length of one side.

Possible Answers:

\(\displaystyle 18\text{in}\)

\(\displaystyle 33\text{in}\)

\(\displaystyle 36\text{in}\)

\(\displaystyle 32\text{in}\)

\(\displaystyle 23\text{in}\)

Correct answer:

\(\displaystyle 23\text{in}\)

Explanation:

The formula to find the perimeter of an equilateral triangle is

\(\displaystyle P = 3a\)

where a is the length of one side of the triangle. Because an equilateral triangle has 3 equal sides, we can use any side in the formula. To find the length of one side, we will solve for a.

Now, we know the perimeter of the triangle is 69in. So, we can substitute and solve for a. We get

\(\displaystyle 69\text{in} = 3a\)

 

\(\displaystyle \frac{69\text{in}}{3} = \frac{3a}{3}\)

 

\(\displaystyle 23\text{in} = a\)

 

\(\displaystyle a = 23\text{in}\)

Therefore, the length of one side of the equilateral triangle is 23in.

Example Question #2 : Triangles

The perimeter of an equilateral triangle is 42cm.  Find the length of one side.

Possible Answers:

\(\displaystyle 14\text{cm}\)

\(\displaystyle 13\text{cm}\)

\(\displaystyle 15\text{cm}\)

\(\displaystyle 12\text{cm}\)

\(\displaystyle 16\text{cm}\)

Correct answer:

\(\displaystyle 14\text{cm}\)

Explanation:

To find the perimeter of an equilateral triangle, we will use the following formula:

\(\displaystyle P = 3a\)

where a is the length of one side. An equilateral triangle has 3 equal sides, so we can use any side in the formula. To find the length of one side, we will solve for a. Now, we know the perimeter of the triangle is 42cm. So, we will substitute and solve for a. We get

\(\displaystyle 42\text{cm} = 3a\)

 

\(\displaystyle \frac{42\text{cm}}{3} = \frac{3a}{3}\)

 

\(\displaystyle 14\text{cm} = a\)

 

\(\displaystyle a = 14\text{cm}\)

Therefore, the length of one side of the equilateral triangle is 14cm.

Example Question #2 : Triangles

A triangle has the sides of \(\displaystyle (x+1)\)\(\displaystyle (1-2x)\), and \(\displaystyle (3x-1)\).  What is the perimeter of the triangle?

Possible Answers:

\(\displaystyle -5x+3\)

\(\displaystyle -2x+1\)

\(\displaystyle 2x-1\)

\(\displaystyle 2x+1\)

\(\displaystyle 5x-3\)

Correct answer:

\(\displaystyle 2x+1\)

Explanation:

The three sides of the triangle are known.  Add all the sides together.

\(\displaystyle (x+1)+ (1-2x)+(3x-1) = 2x+1\)

The answer is:  \(\displaystyle 2x+1\)

Example Question #182 : Geometry And Graphs

Suppose the perimeter of a triangle is \(\displaystyle \frac{1}{3}x-9\). What must be the side length?

Possible Answers:

\(\displaystyle 3x -27\)

\(\displaystyle \frac{1}{9}x -9\)

\(\displaystyle \frac{1}{9}x -3\)

\(\displaystyle 3x-9\)

\(\displaystyle \frac{1}{9}x +9\)

Correct answer:

\(\displaystyle \frac{1}{9}x -3\)

Explanation:

There are three sides in a triangle.

To determine the length of a side, multiply the quantity by one-third.

\(\displaystyle \frac{1}{3}(\frac{1}{3}x-9) = \frac{1}{9}x -3\)

The answer is:  \(\displaystyle \frac{1}{9}x -3\)

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