GED Math : Triangles

Study concepts, example questions & explanations for GED Math

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Example Questions

Example Question #2 : Similar Triangles And Proportions

Which of the following statements follows from the statement  ?

Possible Answers:

Correct answer:

Explanation:

The similarity of two triangles implies nothing about the relationship of two angles of the same triangle. Therefore,  can be eliminated.

The similarity of two triangles implies that corresponding angles between the triangles are congruent. However, because of the positions of the letters,  in  corresponds to , not , in , so . The statement  can be eliminated.

Similarity of two triangles does not imply any congruence between sides of the triangles, so  can be eliminated.

Similarity of triangles implies that corresponding sides are in proportion.  and  in  correspond, respectively, to  and  in . Therefore, it follows that , and this statement is the correct choice.

Example Question #3 : Similar Triangles And Proportions

Triangles

Note: Figure NOT drawn to scale.

Refer to the above diagram. If , which of the following is false?

Possible Answers:

 is a right angle

Correct answer:

Explanation:

Suppose 

Corresponding angles of similar triangles are congruent, so . Also, , so, since  is a right angle, so is .

 

Corresponding sides of similar triangles are in proportion. Since 

the similarity ratio of  to  is 3.

 

By the Pythagorean Theorem, since  is the hypotenuse of a right triangle with legs 6 and 8, its measure is 

.

 , so  is a true statement.

But , so  is false if the triangles are similar. This is the correct choice.

 

Example Question #4 : Similar Triangles And Proportions

Triangles

Note: Figures NOT drawn to scale.

Refer to the above figures. Given that  , evaluate .

Possible Answers:

Correct answer:

Explanation:

By the Pythagorean Theorem, since  is the hypotenuse of a right triangle with legs 6 and 8, its measure is 

.

The similarity ratio of  to  is

.

Likewise, 

Example Question #5 : Similar Triangles And Proportions

Triangles

Note: Figures NOT drawn to scale.

Refer to the above figures. Given that , give the area of .

Possible Answers:

Correct answer:

Explanation:

Corresponding angles of similar triangles are congruent, so, since  is right, so is . This makes  and  the legs of a right triangle, so its area is half their product.

By the Pythagorean Theorem, since  is the hypotenuse of a right triangle with legs 6 and 8, its measure is 

.

The similarity ratio of  to  is

.

This can be used to find  and :

 

 

 

The area of  is therefore 

.

Example Question #6 : Similar Triangles And Proportions

In the figure below, the two triangles are similar. Find the value of .

2

Possible Answers:

Correct answer:

Explanation:

Since the two triangles are similar, we know that their corresponding sides must be in the same ratio to each other. Thus, we can write the following equation:

Now, solve for .

Example Question #1 : Pythagorean Theorem

The two legs of a right triangle measure 30 and 40. What is its perimeter?

Possible Answers:

Correct answer:

Explanation:

By the Pythagorean Theorem, if  are the legs of a right triangle and  is its hypotenuse, 

Substitute  and solve for :

The perimeter of the triangle is 

Example Question #2 : Pythagorean Theorem

A right triangle has legs 30 and 40. Give its perimeter.

Possible Answers:

Correct answer:

Explanation:

The hypotenuse of the right triangle can be calculated using the Pythagorean theorem:

Add the three sides:

Example Question #3 : Pythagorean Theorem

A right triangle has one leg measuring 14 inches; its hypotenuse is 50 inches. Give its perimeter.

Possible Answers:

Correct answer:

Explanation:

The Pythagorean Theorem can be used to derive the length of the second leg:

 inches

Add the three sides to get the perimeter.

 inches.

Example Question #4 : Pythagorean Theorem

Whicih of the following could be the lengths of the sides of a right triangle?

Possible Answers:

10 inches, 1 foot, 14 inches

15 inches, 3 feet, 40 inches

2 feet, 32 inches, 40 inches

7 inches, 2 feet, 30 inches

Correct answer:

2 feet, 32 inches, 40 inches

Explanation:

A triangle is right if and only if it satisfies the Pythagorean relationship

where  is the measure of the longest side and  are the other two sidelengths. We test each of the four sets of lengths, remembering to convert feet to inches by multiplying by 12.

 

7 inches, 2 feet, 30 inches:

2 feet is equal to 24 inches. The relationship to be tested is

 - False

 

10 inches, 1 foot, 14 inches:

1 foot is equal to 12 inches. The relationship to be tested is

 - False

 

15 inches, 3 feet, 40 inches:

3 feet is equal to 36 inches. The relationship to be tested is

 - False

 

2 feet, 32 inches, 40 inches:

2 feet is equal to 24 inches. The relationship to be tested is

 - True

 

The correct choice is 2 feet, 32 inches, 40 inches.

Example Question #5 : Pythagorean Theorem

An isosceles right triangle has hypotenuse 80 inches. Give its perimeter. (If not exact, round to the nearest tenth of an inch.)

Possible Answers:

Correct answer:

Explanation:

Each leg of an isosceles right triangle has length that is the length of the hypotenuse divided by . The hypotenuse has length 80, so each leg has length

.

The perimeter is the sum of the three sides:

 inches.To the nearest tenth:

 inches.

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