Lesson 4: Angles in a Triangle — Practice Questions

1. 1. Two angles in a triangle measure $45^\circ$ and $65^\circ$. What is the measure of the third angle in degrees? ___

2. 2. A right triangle has one angle that measures $22^\circ$. What is the measure of the third angle?

   • A. $22^\circ$
   • B. $68^\circ$
   • C. $90^\circ$
   • D. $158^\circ$

3. 3. An isosceles triangle has a unique angle of $80^\circ$. The other two angles are equal. What is the measure of one of the equal angles in degrees? ___

4. 4. An isosceles triangle has two equal base angles that each measure $55^\circ$. What is the measure of the third, unique angle?

   • A. $55^\circ$
   • B. $125^\circ$
   • C. $70^\circ$
   • D. $110^\circ$

5. 5. Which set of angles could form a valid triangle?

   • A. $60^\circ, 60^\circ, 70^\circ$
   • B. $90^\circ, 45^\circ, 45^\circ$
   • C. $100^\circ, 40^\circ, 50^\circ$
   • D. $30^\circ, 60^\circ, 80^\circ$

6. 6. Lines $a$ and $b$ are parallel and are intersected by a transversal line $c$. If a lower-right angle at one intersection is $75^\circ$, what is the measure in degrees of the corresponding lower-right angle at the other intersection? ___

7. 7. A transversal intersects lines $x$ and $y$. The upper-right angle at the first intersection is $110^\circ$, and the corresponding angle at the second intersection is also $110^\circ$. What can be concluded about lines $x$ and $y$?

   • A. Line $x$ is parallel to line $y$
   • B. Line $x$ is perpendicular to line $y$
   • C. The lines will intersect
   • D. No conclusion can be made

8. 8. Two parallel lines are cut by a transversal. If an angle measures $48^\circ$, what is the measure of its alternate interior angle in degrees? ___

9. 9. A transversal cuts two parallel roads. The angle an on-ramp makes with the first road is $40^\circ$. What is the measure in degrees of the alternate interior angle formed at the second road? ___