Answer Keys: Angles & Angle Measurement

Grade 4 Mathematics | FAST Success Kit

Teacher/Parent Resource: This page contains all answers. Keep separate from student materials.
Student Concept Worksheet Answers
1a. 45 degrees
Acute
1b. 90 degrees
Right
1c. 135 degrees
Obtuse
1d. 180 degrees
Straight
2. The shown angle
Acute
Less than 90 degrees
3. 40 + 50
90 degrees
4. 115 degrees type
Obtuse
Between 90 and 180
5. 90 - 25
65 degrees
Practice Worksheet Answers

Part A: Classify by Measure

1. 75
Acute
2. 90
Right
3. 142
Obtuse
4. 180
Straight
5. 30
Acute
6. 105
Obtuse
7. 89
Acute
8. 168
Obtuse

Part B: Measure with Protractor (Approximate)

9.
~50 degrees
10.
90 degrees
11.
~70 degrees
12.
~110 degrees
13.
~30 degrees
14.
~60 degrees

Part C: Draw Angles

Accept drawings that approximate: 15) 45 degrees (acute), 16) 90 degrees (right angle with square corner), 17) 120 degrees (obtuse), 18) 60 degrees (acute)

Part D: Unknown Angles

19. 180 - 65
115 degrees
20. 90 - 35
55 degrees
21. 130 - 75
55 degrees
22. 180 - 112
68 degrees
23. 90 - 48
42 degrees
24. 180 - 60 - 45
75 degrees

Part E: Angle Addition

25. 35 + 55
90 degrees (Right)
26. 70 + 110
180 degrees (Straight)
27. 45 + 45
90 degrees (Right)
28. 25 + 40 + 25
90 degrees (Right)
29. 60 + 60 + 60
180 degrees (Straight)
30. 90 + 45 + 45
180 degrees (Straight)
FAST Practice Quiz Answers
1
B. Right
A right angle measures exactly 90 degrees, forming a perfect corner or "L" shape.
2
A. Acute
The angle shown is less than 90 degrees (smaller than a right angle), making it acute.
3
C. Obtuse
135 degrees is greater than 90 but less than 180, so it's obtuse.
4
90 degrees
65 + 25 = 90 degrees. Together, these angles form a right angle.
5
C. 108 degrees
Straight angle = 180 degrees. 180 - 72 = 108 degrees for angle Q.
6
A. 47 degrees
Acute angles are less than 90 degrees. Only 47 is less than 90.
7
A. Sarah, because the angle is obtuse and must be greater than 90 degrees
If the angle looks wider than a right angle, it's obtuse (greater than 90). Marcus read the wrong scale on the protractor.
8
45 degrees
Straight angle = 180 degrees. 180 - 55 - 80 = 45 degrees for the third angle.
9
B. 37 degrees
Right angle = 90 degrees. 90 - 53 = 37 degrees.
10
B. Right angle
90 degrees is exactly a right angle - like the corner of a square.

Scoring Guide

Assessment Total Points Proficient (70%+) Needs Support
Student Concept Worksheet 5 points 4+ correct Review angle types
Practice Worksheet 30 points 21+ correct Practice with protractor
FAST Practice Quiz 10 points 7+ correct Focus on angle relationships

Common Errors: Reading wrong protractor scale, thinking ray length affects angle size, confusing acute/obtuse, forgetting that straight angles equal 180 degrees.

FAST Success Kit | Grade 4 | FL B.E.S.T. Standards: MA.4.GR.1.1-1.3