Find Unknown Angle Measures

DOES YOUR ANGLE

MEASURE UP?

You already know how to identify

different types of angles…

#1

Let’s use what we know

about angles to find

missing

measurements.

Angles that share a common ray can be called

adjacent angles.

Angles ABD and DBC are adjacent angles.

#2

Angles ABD and DBC are adjacent angles.

They have the same vertex.

We are given the measure for

angle DBC.

We are looking for the
measure of angle ABD.

How can you find the measure of angle ABC?

Since angles ABD and DBC are adjacent angles, the sum of their

measures will equal the measure of angle ABC.

This means that the measures of angles ABD and DBC added together

will equal the measure of angle ABC.

Angle ABC is a right angle, therefore it measures 90°.

1.Highlight angle

2.

Identify angle

3.

Measure/Solve

What can you do to find the missing measurement?

45° + ____ = 90°
90° - 45° = ____

45°

45°

LET’S TRY ANOTHER ONE!

27° + ____ = 90°

90° - 27° = ____

What do we know about angle EFG?

It’s a right angle, so it measures 90°.

63°

63°

LET’S TRY ANOTHER ONE!

?

21° + ____ = 60°
60° - 21° = ____

If angle KLM measures 60°, what is the measure

of angle KLN?

39°

39°

#3

TRY THIS ONE ON OUR

OWN!

49° + ____ = 120°
120° - 49° = ____

If angle HFG measures 120°, what is the measure of angle HFE?

71°

71°

#4

WORK WITH A PARTNER
OR GROUP TO SOLVE THIS

PROBLEM.

Karen drew an angle that measured 75°. She
drew a ray to divide the angle into two smaller

angles. If one of the new angles measured
46°, what is the measure of the other angle?

46° + ____ = 75°

75° - 46° = ____

29°

#5

Z

Y

V

X

52°
?

Exit Ticket

What’s the measure of angle VYZ?

(Remember: A straight line has a measure of 180°.)

#6