Grade 4 students use the 180 degree rule to find missing angles in triangles. This worksheet provides two angles per triangle and asks learners to subtract their sum from 180 to find the third angle. Fill in the blank items practice the calculation, and a matching activity pairs given angle pairs with the correct missing angle, strengthening number sense and reinforcing the angle sum property of every triangle clearly.
Style:
Classifying Triangles
Part A: Fill in the Blank
Write the missing word or number on each line.
1. If two angles in a triangle measure 60 and 70 degrees, the third angle measures 50 degrees.
2. If two angles in a triangle measure 45 and 45 degrees, the third angle measures 90 degrees.
3. If two angles in a triangle measure 30 and 60 degrees, the third angle measures 90 degrees.
4. A triangle has angles of 80 and 70 degrees. Its third angle measures 30 degrees.
5. If a triangle has angles of 100 and 40 degrees, the third angle measures 40 degrees.
6. A triangle has two angles of 25 and 65 degrees. The third angle measures 90 degrees.
7. If a triangle has angles 110 and 35 degrees, the third angle measures 35 degrees.
8. A triangle has two angles measuring 60 degrees each. The third angle measures 60 degrees.
9. A triangle has angles of 20 and 70 degrees. The third angle measures 90 degrees.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Two angles 50 and 60
→ Third angle 70 degrees
Third angle 70 degrees
Two angles 45 and 45
→ Third angle 90 degrees
Third angle 90 degrees
Two angles 100 and 30
→ Third angle 50 degrees
Third angle 50 degrees
Two angles 80 and 60
→ Third angle 40 degrees
Third angle 40 degrees
Classifying Triangles
★ Part A: Fill in the Blank
Write the missing word or number on each line.
1) If two angles in a triangle measure 60 and 70 degrees, the third angle measures 50 degrees.
2) If two angles in a triangle measure 45 and 45 degrees, the third angle measures 90 degrees.
3) If two angles in a triangle measure 30 and 60 degrees, the third angle measures 90 degrees.
4) A triangle has angles of 80 and 70 degrees. Its third angle measures 30 degrees.
5) If a triangle has angles of 100 and 40 degrees, the third angle measures 40 degrees.
6) A triangle has two angles of 25 and 65 degrees. The third angle measures 90 degrees.
7) If a triangle has angles 110 and 35 degrees, the third angle measures 35 degrees.
8) A triangle has two angles measuring 60 degrees each. The third angle measures 60 degrees.
9) A triangle has angles of 20 and 70 degrees. The third angle measures 90 degrees.
★ Part B: Matching
Match each item on the left to the correct answer on the right.
1) Match each item to its correct answer.
Two angles 50 and 60
→ Third angle 70 degrees
Third angle 70 degrees
Two angles 45 and 45
→ Third angle 90 degrees
Third angle 90 degrees
Two angles 100 and 30
→ Third angle 50 degrees
Third angle 50 degrees
Two angles 80 and 60
→ Third angle 40 degrees
Third angle 40 degrees
Ready to Practice?
Complete each section carefully.
10 Questions
10-15 minutes
Auto-graded
Retry anytime
🏆
Questions Correct
0
Correct
0
Incorrect
0
Skipped
0:00
Time
0%
Score
Review Your Answers
See what you got right, missed, or skipped.