Explanation:
We need to measure each angle shown using a protractor. Remember:
- Place the center of the protractor (the small hole or mark) exactly on the vertex of the angle.
- Align one side of the angle with the 0° line (usually the bottom horizontal line).
- Read the number where the other side crosses the scale.
- Use the inner scale if the angle opens to the right (0° on the right), or outer scale if it opens to the left (0° on the left). But in these diagrams, the 0° is on the right side (standard for most protractors), and angles are measured counterclockwise from 0°.
Let’s go one by one:
1.
Top-left angle:
- One ray points along 0° (right horizontal).
- The other ray points to
130° on the top scale (inner scale, since we go counterclockwise from 0°).
✔ So angle =
130°
2.
Top-right angle:
- One ray at 0° (right).
- Other ray points to
70° (counterclockwise).
✔ So angle =
70°
3.
Middle-left angle:
- One ray at 0° (right).
- Other ray points straight up — that’s
90°.
✔ So angle =
90°
4.
Middle-right angle:
- One ray at 0° (right).
- Other ray points to
20° (just past 0°, small angle).
✔ So angle =
20°
5.
Bottom angle (two rays):
- This is an angle formed by two rays both going upward — one at
40°, the other at
140° (both measured from 0° on the right, counterclockwise).
- To find the angle between them: subtract the smaller from the larger:
140° − 40° =
100°
✔ So angle =
100°
Double-check:
- 130°, 70°, 90°, 20°, 100° — all are reasonable, less than or equal to 180°, as expected for protractor use.
Final Answer:
130°, 70°, 90°, 20°, 100°
Parent Tip: Review the logic above to help your child master the concept of measuring angles worksheet 4th grade.
