Students fix three protractor and classification errors — reading 120° instead of 60° due to wrong scale, a straight angle called 360°, and 75° misclassified as a right angle. Part B has four fill-in-the-blank questions about degrees, protractor placement, and right angles. Part C has two short-answer questions about protractor setup steps and why protractors have two scales.
Understanding why a protractor has two scales prevents the most persistent measurement error at this level.
Style:
Angles and Angle Measurement
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
The angle measures 120° because the ray points to 120 on the protractor.
Rewrite: The angle measures 60° because you must read from the scale that starts at 0° on the base ray.
2. Fix the sentence:
A straight angle measures 360° because the rays form a line.
Rewrite: A straight angle measures 180° because the rays point in opposite directions forming a line.
3. Fix the sentence:
An angle of 75° is a right angle because it is close to 90°.
Rewrite: An angle of 75° is an acute angle because it is less than 90°.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. A protractor measures angles in units called degrees.
2. To measure an angle, place the center of the protractor on the vertex.
3. An angle measuring exactly 90° is called a right angle.
4. A full turn around a point measures 360 degrees.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. Explain the two steps for placing a protractor to measure an angle.
First, place the center point of the protractor on the vertex of the angle. Then align the base line of the protractor with one ray of the angle.
2. Why does a protractor have two scales of numbers?
A protractor has two scales so you can measure an angle from either direction. You use the scale that starts at 0° on the ray you aligned.
Angles and Angle Measurement
★ Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1) Fix the sentence:
The angle measures 120° because the ray points to 120 on the protractor.
Rewrite: The angle measures 60° because you must read from the scale that starts at 0° on the base ray.
2) Fix the sentence:
A straight angle measures 360° because the rays form a line.
Rewrite: A straight angle measures 180° because the rays point in opposite directions forming a line.
3) Fix the sentence:
An angle of 75° is a right angle because it is close to 90°.
Rewrite: An angle of 75° is an acute angle because it is less than 90°.
★ Part B: Fill in the Blank
Write the missing word or number on each line.
1) A protractor measures angles in units called degrees.
2) To measure an angle, place the center of the protractor on the vertex.
3) An angle measuring exactly 90° is called a right angle.
4) A full turn around a point measures 360 degrees.
★ Part C: Short Answer
Answer each question in one or two complete sentences.
1) Explain the two steps for placing a protractor to measure an angle.
First, place the center point of the protractor on the vertex of the angle. Then align the base line of the protractor with one ray of the angle.
2) Why does a protractor have two scales of numbers?
A protractor has two scales so you can measure an angle from either direction. You use the scale that starts at 0° on the ray you aligned.
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15-20 minutes
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