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This printable supports Common Core Mathematics Standard 8.G.A.5

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# Exterior Angles of Triangles (Grade 8)

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## Exterior Angles of Triangles

1.
What is the sum of the exterior angles of a triangle?
1. $180deg$
2. $270deg$
3. $360deg$
4. $540deg$
2.
The exterior angle of a triangle is equal to
1. the value of its adjacent angle.
2. the sum of its opposite interior angles.
3. the product of its opposite interior angles.
4. the difference between its opposite interior angles.
3.
Which of the following statements about the exterior angle of a triangle is true?
1. It is always equal to the value of its adjacent angle.
2. It is always larger than either opposite interior angle.
3. It is always larger than the sum of its opposite interior angles.
4. It is always equal to the sum of the interior angles of the triangle.
4.
What is the measure of one external angle of an equilateral triangle?
1. $30deg$
2. $60deg$
3. $120deg$
4. $180deg$
5.
The measures of the angles of triangle ABC are:

$angA = xdeg$
$angB = ydeg$
$angC = zdeg$

Extend side AC to the right to form an external angle. Which expression equals the value of the external angle? 1. $y - z$
2. $y + z$
3. $x - y$
4. $x + y$
6.
An external angle of a triangle is $80deg$. Which of the following could be a value of one of its opposite interior angles?
1. $50deg$
2. $80deg$
3. $100deg$
4. $120deg$
7.
Extend $bar (AC$ to the right of C to create an exterior angle adjacent to C. If $angA = 100deg$ and $angB = 25deg$, what is the value of the exterior angle adjacent to C? 1. $55deg$
2. $75deg$
3. $100deg$
4. $125deg$
8.
Triangle ABC is isosceles and its vertex is B. If $angB = 30deg$, what is the measure of an external base angle of the triangle? 1. $45deg$
2. $75deg$
3. $105deg$
4. $150deg$
9.
The exterior base angles of an isosceles triangle each measure $100deg$. What is the measure of the interior vertex angle of the triangle?
1. $20deg$
2. $60deg$
3. $80deg$
4. $160deg$
10.
Extend line AC to the right and place point D on the extended line to create line ACD. Given the following:

$mangBCD = 115deg$
$mangB = 90deg$
$mangA = xdeg$

Which equation can be used to solve for $mangA$? 1. $90 + x = 115$
2. $65 + x = 115$
3. $65 - x = 115$
4. $90 - x = 115$        You need to be a HelpTeaching.com member to access free printables.