Let's solve this step-by-step. The task is to
estimate the size of each angle, identify its
type, and write its
notation (using the vertex and points on each side).
---
🔍 Step 1: Understand the Angle Types
-
Acute: Less than 90°
-
Right: Exactly 90°
-
Obtuse: Greater than 90° but less than 180°
-
Reflex: Greater than 180° but less than 360°
---
We’ll go through each angle one by one.
---
🔹 Example: ∠ABC
Given:
- Estimate: 35°
- Type: ACUTE
- Notation: ∠ABC
✔ This is correct — small angle, less than 90°.
---
🔹 1. ∠DEF
Looking at the diagram:
- The angle at E between D and F is
small, like the example.
- It looks
less than 90°, maybe around
40–50°.
- So it’s
acute.
- Notation: ∠DEF
✔ Estimate: 45°
✔ Type: ACUTE
✔ Notation: ∠DEF
---
🔹 2. ∠GIH
- The angle at I between G and H is
very narrow, even smaller than the first.
- Looks like about
20–25°
- Definitely
acute
- Notation: ∠GIH
✔ Estimate: 25°
✔ Type: ACUTE
✔ Notation: ∠GIH
---
🔹 3. ∠JKL
- At point K, between J and L.
- Looks
wider than 90°, but not too wide.
- Seems like
110–120°
- So
obtuse
- Notation: ∠JKL
✔ Estimate: 110°
✔ Type: OBTUSE
✔ Notation: ∠JKL
---
🔹 4. ∠NMO
- At M, with rays going to N and O.
- There's a
curved arc indicating the angle, and it's
greater than 180° (reflex).
- It looks like it wraps more than half a circle.
- Estimate: ~250°
- Type:
REFLEX
- Notation: ∠NMO
✔ Estimate: 250°
✔ Type: REFLEX
✔ Notation: ∠NMO
---
🔹 5. ∠PRQ
- At R, between P and Q.
- Looks like a
standard V shape, but not too sharp.
- Around
70–80°
- Still
acute
- Notation: ∠PRQ
✔ Estimate: 75°
✔ Type: ACUTE
✔ Notation: ∠PRQ
---
🔹 6. ∠SUT
- At U, between S and T.
- Looks
wide, but not as wide as the previous obtuse one.
- About
100–110°
- So
obtuse
- Notation: ∠SUT
✔ Estimate: 105°
✔ Type: OBTUSE
✔ Notation: ∠SUT
---
🔹 7. ∠XWV
- At W, between X and V.
- There’s a
square corner symbol, which means
exactly 90°
- So it's a
right angle
- Notation: ∠XWV
✔ Estimate: 90°
✔ Type: RIGHT
✔ Notation: ∠XWV
---
🔹 8. ∠AZY
- At Z, between A and Y.
- The angle looks
large, greater than 90°, but less than 180°.
- Probably around
130–140°
- So
obtuse
- Notation: ∠AZY
✔ Estimate: 135°
✔ Type: OBTUSE
✔ Notation: ∠AZY
---
🔹 9. ∠TPE
- At P, between T and E.
- The angle is
greater than 180°, because it curves the long way around.
- It looks like about
220–230°
- So
reflex
- Notation: ∠TPE
✔ Estimate: 220°
✔ Type: REFLEX
✔ Notation: ∠TPE
---
✔ Final Table Summary:
| Angle | Estimate | Type | Notation |
|-------|----------|----------|----------|
| ∠DEF | 45° | ACUTE | ∠DEF |
| ∠GIH | 25° | ACUTE | ∠GIH |
| ∠JKL | 110° | OBTUSE | ∠JKL |
| ∠NMO | 250° | REFLEX | ∠NMO |
| ∠PRQ | 75° | ACUTE | ∠PRQ |
| ∠SUT | 105° | OBTUSE | ∠SUT |
| ∠XWV | 90° | RIGHT | ∠XWV |
| ∠AZY | 135° | OBTUSE | ∠AZY |
| ∠TPE | 220° | REFLEX | ∠TPE |
---
📝 Notes:
-
Estimates are approximate since no protractor is used.
-
Notation always uses three letters: the middle letter is the
vertex.
- Always check if the angle is reflex (greater than 180°) or just obtuse.
Let me know if you'd like a printable version or visual explanation!
Parent Tip: Review the logic above to help your child master the concept of 4th grade angles worksheet.