HSPT Math : How to find the measure of an angle

Study concepts, example questions & explanations for HSPT Math

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Example Questions

Example Question #1 : How To Find The Measure Of An Angle

What is the sum of the interior angles of a triangle?

Possible Answers:

Correct answer:

Explanation:

The sum of the three interior angles of a triangle is  degrees.

Example Question #1 : How To Find The Measure Of An Angle

Two of the interior angles of a triangle measure  and . What is the greatest measure of any of its exterior angles?

Possible Answers:

It cannot be determined from the information given.

Correct answer:

Explanation:

The interior angles of a triangle must have measures whose sum is , so the measure of the third angle must be .

By the Triangle Exterior-Angle Theorem, an exterior angle of a triangle measures the sum of its remote interior angles; therefore, to get the greatest measure of any exterior angle, we add the two greatest interior angle measures: 

Example Question #1 : How To Find An Angle Of A Line

Two angles are supplementary and have a ratio of 1:4.  What is the size of the smaller angle?

Possible Answers:

45^{\circ}

72^{\circ}

144^{\circ}

36^{\circ}

18^{\circ}

Correct answer:

36^{\circ}

Explanation:

Since the angles are supplementary, their sum is 180 degrees.  Because they are in a ratio of 1:4, the following expression could be written:

x+4x=180

5x=180

x=36^{\circ}

Example Question #1 : Acute / Obtuse Triangles

In a given triangle, the angles are in a ratio of 1:3:5.  What size is the middle angle?

Possible Answers:

45^{\circ}

60^{\circ}

75^{\circ}

20^{\circ}

90^{\circ}

Correct answer:

60^{\circ}

Explanation:

Since the sum of the angles of a triangle is 180^{\circ}, and given that the angles are in a ratio of 1:3:5, let the measure of the smallest angle be , then the following expression could be written:

x+3x+5x=180

9x=180

x=20

 

If the smallest angle is 20 degrees, then given that the middle angle is in ratio of 1:3, the middle angle would be 3 times as large, or 60 degrees.

Example Question #1 : Right Triangles

The measure of 3 angles in a triangle are in a 1:2:3 ratio. What is the measure of the middle angle?

Possible Answers:
30
90
60
45
Correct answer: 60
Explanation:

The angles in a triangle sum to 180 degrees. This makes the middle angle 60 degrees.

Example Question #3 : How To Find The Measure Of An Angle

Call the three angles of a triangle 

The measure of  is twenty degrees greater than that of ; the measure of  is thirty degrees less than twice that of . If  is the measure of , then which of the following equations would we need to solve in order to calculate the measures of the angles?

Possible Answers:

Correct answer:

Explanation:

The measure of  is twenty degrees greater than the measure  of , so its measure is 20 added to that of  - that is, .

The measure of  is thirty degrees less than twice that of . Twice the measure of  is , and thirty degrees less than this is 30 subtracted from  - that is, .

The sum of the measures of the three angles of a triangle is 180, so, to solve for  - thereby allowing us to calulate all three angle measures - we add these three expressions and set the sum equal to 180. This yields the equation:

Example Question #4 : How To Find The Measure Of An Angle

Call the three angles of a triangle 

The measure of  is forty degrees less than that of ; the measure of  is ten degrees less than twice that of . If  is the measure of , then which of the following equations would we need to solve in order to calculate the measures of the angles?

Possible Answers:

Correct answer:

Explanation:

The measure of  is forty degrees less than the measure  of , so its measure is 40 subtracted from that of  - that is, .

The measure of  is ten degrees less than twice that of . Twice the measure of  is , and ten degrees less than this is 10 subtracted from  - that is, .

The sum of the measures of the three angles of a triangle is 180, so, to solve for  - thereby allowing us to calulate all three angle measures - we add these three expressions and set the sum equal to 180. This yields the equation:

Example Question #4 : How To Find The Measure Of An Angle

Two interior angles of a triangle adds up to  degrees.  What is the measure of the other angle?

Possible Answers:

Correct answer:

Explanation:

The sum of the three angles of a triangle add up to 180 degrees.  Subtract 64 degrees to determine the third angle.

Example Question #1 : How To Find The Measure Of An Angle

What is  of the measure of a right angle?

Possible Answers:

Correct answer:

Explanation:

A right angle has a measure of .  One fifth of the angle is:

Example Question #6 : How To Find The Measure Of An Angle

What angle is complementary to ?

Possible Answers:

Correct answer:

Explanation:

To find the other angle, subtract the given angle from  since complementary angles add up to .

The complementary is:

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