Name
LESSON
Date
Class
Practice C
9-4 Finding Angle Measures
Classify each pair of angles as complementary or
supplementary. Then find the missing angle measure.
1.
2.
x
122° x
35°
Find each unknown angle measure.
3. 1 and 2 are vertical angles.
1 measures 48°.
4. 3 and 4 are supplementary
angles. 4 measures 117°.
5. 7 and 8 are complementary
angles. 7 measures 23°.
6. 5 and 6 are congruent angles.
6 measures 12.5°.
7. Angles L and M are complementary. If mL is 16o,
what is mM?
8. Angles R and S are supplementary. If mR is 78o,
what is mS?
9. If 1 and 2 are supplementary angles, and 3 and 2 are
supplementary angles, what do you know about 1 and 3?
Explain.
10. Two angles are complementary. One angle is 20° smaller than
the other angle. What are the measures of both angles?
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
31
Holt Mathematics
Practice B
9-4 Finding Angle Measures
Practice A
9-4 Finding Angle Measures
LESSON
LESSON
Identify the type of each angle pair shown.
Choose the correct answer.
1. In the figure below, mABC 180°.
What is the unknown angle
measurement?
1.
2. The angle pair shown below are
supplementary angles. What is the
unknown angle measurement?
2.
30° 15°
30°
60°
70°
72°
A
A 18°
B 36°
C 72°
D 90°
complementary angles
72°
B
C
F 20°
G 90°
H 110°
J 70°
25°
?
50°
F 25°
A 50°
B 40°
G 65°
H 155°
J 50°
C 130°
D 90°
4. The angles are complementary.
3. The angles are supplementary.
5. Angles G and H are supplementary. If mG is 80o,
what is mH?
100°
6. Angles M and N are complementary. If mM is 20o,
what is mN?
2
2 120°
4. The angles shown below are vertical
angles. What is the unknown angle
measurement?
3. The angle pair shown below are
complementary angles. What is the
unknown angle measurement?
adjacent angles
Find each unknown angle measure.
35°
m2 60°
m2 55°
5. Angles W and X are supplementary. If mW is 37o,
what is mX?
143°
6. Angles S and T are complementary. If mS is 64o,
what is mT?
26°
7. Angles C and D are supplementary. If mC is 83o,
what is mD?
97°
8. Angles U and V are complementary. If mU is 41o,
what is mV?
49°
9. Is the following statement always true, sometimes true, or
never true? Explain your reasoning. Two congruent angles
that are complementary both measure 45°.
70°
7. Kelly subtracts 60° from 90° to find the measure of a missing
angle in an angle pair. What type of angle pair is she working
with?
It is always true. Congruent angles have the same measure, and the sum
of two complementary angles is 90°; 90° 2 45°.
complementary angles
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
29
Holt Mathematics
Practice C
9-4 Finding Angle Measures
30
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
Holt Mathematics
Review for Mastery
9-4 Finding Angle Measures
LESSON
LESSON
Classify each pair of angles as complementary or
supplementary. Then find the missing angle measure.
1.
You can use related facts to find an unknown angle measure.
If you know that angles J and K are supplementary and mJ 78°,
you can find the measure of angle K.
2.
x
122° x
35°
supplementary; 58°
J
complementary; 55°
K
First write an equation.
Find each unknown angle measure.
3. 1 and 2 are vertical angles.
1 measures 48°.
78 K 180 Supplementary angles have a sum of 180°.
4. 3 and 4 are supplementary
angles. 4 measures 117°.
m2 48°
Then use related facts to solve the equation.
78 K 180
Think: 180 78 K
K 102
m3 63°
5. 7 and 8 are complementary
angles. 7 measures 23°.
6. 5 and 6 are congruent angles.
6 measures 12.5°.
m8 67°
So, the measure of angle K 102°.
m5 12.5°
Find each unknown angle measure.
7. Angles L and M are complementary. If mL is 16o,
what is mM?
74°
8. Angles R and S are supplementary. If mR is 78o,
what is mS?
102°
1. The angles are supplementary.
2. The angles are complementary.
T
C
9. If 1 and 2 are supplementary angles, and 3 and 2 are
supplementary angles, what do you know about 1 and 3?
Explain.
V
66°
D
The measure of 1 equals the measure of 3. m1 m2 180°,
so m1 180° m2. m3 m2 180°, so m3 180° m2.
Therefore, m3 m1.
B
A
U
mABC 114°
mTUV 62°
3. The angles are vertical angles.
4. The angles are supplementary.
X
10. Two angles are complementary. One angle is 20° smaller than
the other angle. What are the measures of both angles?
76°
V 2 Y
Z
35° and 55
95°
G
W
m2 76°
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
28°
W
31
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
Holt Mathematics
Copyright © by Holt, Rinehart and Winston.
All rights reserved.
103
H
mH 85°
32
Holt Mathematics
Holt Mathematics