Let’s go step by step to measure each angle using the protractor shown in the worksheet.
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Part 1: Measure the angles below
We look at where the red line crosses the protractor scale. Remember:
- The bottom red line is always on the 0° mark (either left or right side).
- We read the number where the top red line points — that’s the angle size.
- Since these are all acute angles (less than 90°), we pick the smaller number on the protractor.
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a)
The top line points to
40° on the inner scale (since the bottom line is on the right 0°).
→ Angle =
40°
b)
Top line points straight up to
90°.
→ Angle =
90°
c)
Top line points to
80° on the inner scale (bottom line on right 0°).
→ Angle =
80°
d)
Top line points to
20° on the inner scale (bottom line on right 0°).
→ Angle =
20°
e)
Top line points to
70° on the inner scale (bottom line on left 0° — so we use the outer scale? Wait, let’s check carefully.)
Actually, in diagram e), the bottom line is on the
left 0°, and the top line goes to
70° on the
outer scale (which starts from left 0° going clockwise). But since it’s an acute angle, and the line is between 60° and 80°, it’s clearly
70°.
Wait — actually, looking again: if the baseline is on the left 0°, then we read the outer scale. The top line hits exactly at
70° on the outer scale. So yes,
70°.
But wait — let me double-check with the image logic: In most protractors, if you start from the left 0°, you read the outer numbers. The line is pointing to 70° on the outer ring → correct.
→ Angle =
70°
f)
Bottom line is on the right 0°, top line points to
45° on the inner scale (between 40° and 50°).
→ Angle =
45°
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Now Part 2: Circle the most likely measurement.
These are not measured with a protractor — we estimate based on how wide the angle looks.
a) This angle is small — much less than 90°. Looks like about 30°.
Options: 130°, 30°, 90° → Pick
30°
b) This angle is also acute — looks like it’s around 70°, maybe a bit more. Not 95° (that’s obtuse) or 180° (straight line).
Options: 95°, 180°, 70° → Pick
70°
c) This angle is very close to 90°, but slightly less. 85° makes sense. 250° and 110° are way too big.
Options: 85°, 250°, 110° → Pick
85°
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Final Answer:
1.
a) 40°
b) 90°
c) 80°
d) 20°
e) 70°
f) 45°
2.
a) 30°
b) 70°
c) 85°
Parent Tip: Review the logic above to help your child master the concept of protractor worksheet 4th grade.
