Angles and Angle Measurement — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Two angles on a straight line add up to 180 degrees.
Angles on a straight line are supplementary and always sum to 180°.
2. If angle A is 72° and angle B together with A makes a straight angle, then angle B is 108 degrees.
180 − 72 = 108°.
3. A right angle split into two equal parts makes two angles of 45 degrees each.
90 ÷ 2 = 45°.
4. An angle of 38° and an unknown angle form a right angle. The unknown angle is 52 degrees.
90 − 38 = 52°.
5. Three angles of 60° each make a straight angle.
3 × 60° = 180°, which is a straight angle.
6. An obtuse angle must measure more than 90° but less than 180 degrees.
Obtuse angles range from greater than 90° up to (but not including) 180°.
7. If a straight angle is split into angles of 95° and x°, then x = 85.
180 − 95 = 85°.
8. Two complementary angles add up to 90 degrees.
Complementary angles always sum to exactly 90°.
9. A half turn is the same as a straight angle.
A half turn = 180° = a straight angle.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Corner of a book
→ 90°
30°
Hands of a clock at 2:00
→ 60°
90°
Slice of pizza tip
→ 30°
60°
Wide-open scissors
→ 150°
150°
Corner of book → 90°; Clock at 2:00 → 60°; Pizza slice tip → 30°; Wide scissors → 150°.