Identifying Acute, Obtuse And Right Angles With Angle Marks (A) - Free Printable

To solve the problem of identifying each angle as acute, obtuse, or right, we need to understand the definitions of these types of angles:

1. Acute Angle: An angle that measures less than 90 degrees.
2. Right Angle: An angle that measures exactly 90 degrees.
3. Obtuse Angle: An angle that measures more than 90 degrees but less than 180 degrees.

Now, let's analyze each angle in the image step by step:

Row 1:

1. Acute
2. Right
3. Obtuse
4. Obtuse

Row 2:

5. Obtuse
6. Acute
7. Acute
8. Acute

Row 3:

9. Acute
10. Obtuse
11. Acute
12. Obtuse

Row 4:

13. Acute
14. Obtuse
15. Obtuse
16. Obtuse

Row 5:

17. Obtuse
18. Right
19. Obtuse
20. Straight (Note: This is not one of the options, but it's important to recognize it)

Final Answer:

- Acute: 1, 6, 7, 9, 10, 13, 18, 20
- Right: 2, 18
- Obtuse: 3, 4, 5, 8, 11, 12, 14, 15, 16, 17, 19

So, the solution is:

\[
\boxed{
\text{Acute: 1, 6, 7, 9, 10, 13, 18, 20; Right: 2, 18; Obtuse: 3, 4, 5, 8, 11, 12, 14, 15, 16, 17, 19}
}
\]