Students correct three classification errors — 120° called acute, a right angle measuring 100°, and 45° called obtuse. Part B has four fill-in-the-blank questions about acute, straight, and right angle definitions. Part C has two short-answer questions about distinguishing acute from obtuse angles and naming classroom objects with right angles.
Correcting common misclassifications builds the habit of using degree benchmarks rather than visual estimates.
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:
A 120° angle is an acute angle because it is more than 90°.
Rewrite: A 120° angle is an obtuse angle because it is more than 90° but less than 180°.
2. Fix the sentence:
A right angle measures exactly 100°.
Rewrite: A right angle measures exactly 90°.
3. Fix the sentence:
A 45° angle is obtuse because 45 is less than 90.
Rewrite: A 45° angle is acute because it measures less than 90°.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. An angle that measures less than 90° is called acute.
2. An angle that measures exactly 180° is called a straight angle.
3. The corner of a book forms a right angle.
4. An angle measuring 135° is classified as obtuse.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. How can you tell the difference between an acute angle and an obtuse angle?
An acute angle measures less than 90° and looks narrow, while an obtuse angle measures more than 90° but less than 180° and looks wide.
2. Name two objects in a classroom that have right angles.
The corner of a desk and the corner of a whiteboard both have right angles because they measure exactly 90°.
Angles and Angle Measurement
★ Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1) Fix the sentence:
A 120° angle is an acute angle because it is more than 90°.
Rewrite: A 120° angle is an obtuse angle because it is more than 90° but less than 180°.
2) Fix the sentence:
A right angle measures exactly 100°.
Rewrite: A right angle measures exactly 90°.
3) Fix the sentence:
A 45° angle is obtuse because 45 is less than 90.
Rewrite: A 45° angle is acute because it measures less than 90°.
★ Part B: Fill in the Blank
Write the missing word or number on each line.
1) An angle that measures less than 90° is called acute.
2) An angle that measures exactly 180° is called a straight angle.
3) The corner of a book forms a right angle.
4) An angle measuring 135° is classified as obtuse.
★ Part C: Short Answer
Answer each question in one or two complete sentences.
1) How can you tell the difference between an acute angle and an obtuse angle?
An acute angle measures less than 90° and looks narrow, while an obtuse angle measures more than 90° but less than 180° and looks wide.
2) Name two objects in a classroom that have right angles.
The corner of a desk and the corner of a whiteboard both have right angles because they measure exactly 90°.
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9 Questions
15-20 minutes
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