High School Math : High School Math

Study concepts, example questions & explanations for High School Math

varsity tutors app store varsity tutors android store

Example Questions

Example Question #2 : Isosceles Triangles

The base angle of an isosceles triangle is 10 more than twice the vertex angle.  What is the vertex angle?

Possible Answers:

Correct answer:

Explanation:

Every triangle has 180 degrees.  An isosceles triangle has one vertex angle and two congruent base angles.

Let = the vertex angle and  = the base angle

So the equation to solve becomes

The vertex angle is 32 degrees and the base angle is 74 degrees

Example Question #6 : How To Find An Angle In An Acute / Obtuse Triangle

In an isosceles triangle, the vertex angle is 15 less than the base angle.  What is the base angle?

Possible Answers:

Correct answer:

Explanation:

Every triangle has 180 degrees.  An isosceles triangle has one vertex angle and two congruent base angles.

Let  = base angle and  = vertex angle

So the equation to solve becomes

Thus, 65 is the base angle and 50 is the vertex angle.

Example Question #11 : Isosceles Triangles

In an isosceles triangle the vertex angle is half the base angle.  What is the vertex angle?

Possible Answers:

108

54

45

36

72

Correct answer:

36

Explanation:

Every triangle has 180 degrees.  An isosceles triangle has one vertex angle and two congruent base angles.

Let x = base angle and 0.5x = vertex angle

So the equation to solve becomes x+x+0.5x=180, thus x=72 is the base angle and 0.5x=36 is the vertex angle.

Example Question #101 : Triangles

If the average of the measures of two angles in a triangle is 75o, what is the measure of the third angle in this triangle?

Possible Answers:

40°

75°

50°

30°

65°

Correct answer:

30°

Explanation:

The sum of the angles in a triangle is 180o:  a + b + c = 180

In this case, the average of a and b is 75:

(a + b)/2 = 75, then multiply both sides by 2

(a + b) = 150, then substitute into first equation

150 + c = 180

c = 30

Example Question #2 : Acute / Obtuse Triangles

Which of the following can NOT be the angles of a triangle?

Possible Answers:

30.5, 40.1, 109.4

45, 90, 100

45, 45, 90

30, 60, 90

1, 2, 177

Correct answer:

45, 90, 100

Explanation:

In a triangle, there can only be one obtuse angle. Additionally, all the angle measures must add up to 180.

Example Question #3 : Acute / Obtuse Triangles

 

 

Let the measures, in degrees, of the three angles of a triangle be x, y, and z. If y = 2z, and z = 0.5x - 30, then what is the measure, in degrees, of the largest angle in the triangle?

 

Possible Answers:
96
108
48
60
30
Correct answer: 108
Explanation:

The measures of the three angles are x, y, and z. Because the sum of the measures of the angles in any triangle must be 180 degrees, we know that x + y + z = 180. We can use this equation, along with the other two equations given, to form this system of equations:

x + y + z = 180

y = 2z

z = 0.5x - 30

If we can solve for both y and x in terms of z, then we can substitute these values into the first equation and create an equation with only one variable.

Because we are told already that y = 2z, we alreay have the value of y in terms of z.

We must solve the equation z = 0.5x - 30 for x in terms of z.

Add thirty to both sides.

z + 30 = 0.5x

Mutliply both sides by 2

2(z + 30) = 2z + 60 = x

x = 2z + 60

Now we have the values of x and y in terms of z. Let's substitute these values for x and y into the equation x + y + z = 180.

(2z + 60) + 2z + z = 180

5z + 60 = 180

5z = 120

z = 24

Because y = 2z, we know that y = 2(24) = 48. We also determined earlier that x = 2z + 60, so x = 2(24) + 60 = 108.

Thus, the measures of the three angles of the triangle are 24, 48, and 108. The question asks for the largest of these measures, which is 108.

The answer is 108. 

Example Question #4 : Acute / Obtuse Triangles

Angles x, y, and z make up the interior angles of a scalene triangle. Angle x is three times the size of y and 1/2 the size of z. How big is angle y.

Possible Answers:

42

36

108

54

18

Correct answer:

18

Explanation:

The answer is 18

We know that the sum of all the angles is 180. Using the rest of the information given we can write the other two equations:

x + y + z = 180      

x = 3y      

2x = z

We can solve for y and z in the second and third equations and then plug into the first to solve.

x + (1/3)x + 2x = 180

3[x + (1/3)x + 2x = 180]

3x + x + 6x = 540

10x = 540

x = 54

y = 18

z = 108

Example Question #121 : Triangles

Slide2

In the picture above,  is a straight line segment. Find the value of .

Possible Answers:

Correct answer:

Explanation:

A straight line segment has 180 degrees. Therefore, the angle that is not labelled must have:

We know that the sum of the angles in a triangle is 180 degrees. As a result, we can set up the following algebraic equation:

Subtract 70 from both sides:

Divide by 2:

Example Question #21 : Acute / Obtuse Triangles

Rt_triangle_lettersIf angle  and angle , what is the value of ?

Possible Answers:

Correct answer:

Explanation:

For this problem, remember that the sum of the degrees in a triangle is .

This means that .

Plug in our given values to solve:

Example Question #22 : Acute / Obtuse Triangles

In , and . To the nearest tenth, what is  ?

Possible Answers:

A triangle with these sidelengths cannot exist.

Correct answer:

A triangle with these sidelengths cannot exist.

Explanation:

The sum of the two smallest sides is less than the greatest side:

By the Triangle Inequality, this triangle cannot exist.

Learning Tools by Varsity Tutors