Fourth graders sort out the classic mix-up between complementary and supplementary angles, then prove they have got it by fixing sentences like "angles that add up to 180° are complementary" and "the supplement of 60° is 30°." They also rescue a 150° angle that was wrongly called acute.
Fill-in lines ask for the complement of 50°, the supplement of 135°, and the name for any angle between 0° and 90°. Two short-answer prompts push students to explain how supplementary angles work when one piece is 70°. Once these patterns click, finding missing angles becomes quick mental math.
Style:
Angles and Measurement
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
Two angles that add up to 180° are called complementary angles.
Rewrite: Two angles that add up to 180° are called supplementary angles.
2. Fix the sentence:
The supplement of a 60° angle is 30° because 60 minus 30 equals 30.
Rewrite: The supplement of a 60° angle is 120° because 180° minus 60° equals 120°.
3. Fix the sentence:
A 150° angle is acute because it is a large number.
Rewrite: A 150° angle is obtuse because it is greater than 90° but less than 180°.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. Two angles that add up to 180° are called supplementary angles.
2. The complement of a 50° angle is 40 degrees.
3. The supplement of a 135° angle is 45 degrees.
4. An angle between 0° and 90° is always acute.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. What is the difference between complementary and supplementary angles?
Complementary angles add up to 90°, while supplementary angles add up to 180°.
2. If two angles are supplementary and one is 70°, explain how to find the other angle.
Subtract 70° from 180° to get 110°. Since supplementary angles add up to 180°, the other angle must be 110°.
Angles and Measurement
★ Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1) Fix the sentence:
Two angles that add up to 180° are called complementary angles.
Rewrite: Two angles that add up to 180° are called supplementary angles.
2) Fix the sentence:
The supplement of a 60° angle is 30° because 60 minus 30 equals 30.
Rewrite: The supplement of a 60° angle is 120° because 180° minus 60° equals 120°.
3) Fix the sentence:
A 150° angle is acute because it is a large number.
Rewrite: A 150° angle is obtuse because it is greater than 90° but less than 180°.
★ Part B: Fill in the Blank
Write the missing word or number on each line.
1) Two angles that add up to 180° are called supplementary angles.
2) The complement of a 50° angle is 40 degrees.
3) The supplement of a 135° angle is 45 degrees.
4) An angle between 0° and 90° is always acute.
★ Part C: Short Answer
Answer each question in one or two complete sentences.
1) What is the difference between complementary and supplementary angles?
Complementary angles add up to 90°, while supplementary angles add up to 180°.
2) If two angles are supplementary and one is 70°, explain how to find the other angle.
Subtract 70° from 180° to get 110°. Since supplementary angles add up to 180°, the other angle must be 110°.
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15-20 minutes
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