Grade 4 students explore triangle angles using familiar references in this worksheet. Learners use the corner of a piece of paper to identify right angles and read clock-hand angles to classify triangles as acute, right, or obtuse. Spelling correction items fix grammar mistakes about angle classifications, fill in the blank questions strengthen angle vocabulary, and short answer prompts ask students to explain their reasoning clearly.
Style:
Classifying Triangles
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
The corner of a piece of paper measures 60 degrees, so a triangle with that angle is acute.
Rewrite: The corner of a piece of paper measures 90 degrees, so a triangle with that angle is a right triangle.
2. Fix the sentence:
A triangle whose largest angle measures 110 degrees is classify as an acute triangle.
Rewrite: A triangle whose largest angle measures 110 degrees is classified as an obtuse triangle.
3. Fix the sentence:
If all three angles in a triangle measure less than 90 degrees, the triangle is a right triangle.
Rewrite: If all three angles in a triangle measure less than 90 degrees, the triangle is an acute triangle.
Part B: Fill in the Blank
Write the missing word or number on each line.
1. The corner of a piece of paper forms a right angle that measures 90 degrees.
2. A triangle that contains exactly one 90 degree angle is called a right triangle.
3. When the hour hand points to 12 and the minute hand points to 3, the hands form a right angle.
4. A triangle with one angle measuring 120 degrees must be classified as an obtuse triangle.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. How can the corner of a piece of paper help you decide if a triangle has a right angle?
I can place the paper corner against a triangle vertex. If it fits exactly, that angle is 90 degrees, so the triangle is a right triangle.
2. A clock shows 9:00. What kind of angle do the hour and minute hands form, and why?
At 9:00 the hands form a right angle of 90 degrees because the minute hand points to 12 and the hour hand points to 9, making a quarter turn apart.
Classifying Triangles
★ Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1) Fix the sentence:
The corner of a piece of paper measures 60 degrees, so a triangle with that angle is acute.
Rewrite: The corner of a piece of paper measures 90 degrees, so a triangle with that angle is a right triangle.
2) Fix the sentence:
A triangle whose largest angle measures 110 degrees is classify as an acute triangle.
Rewrite: A triangle whose largest angle measures 110 degrees is classified as an obtuse triangle.
3) Fix the sentence:
If all three angles in a triangle measure less than 90 degrees, the triangle is a right triangle.
Rewrite: If all three angles in a triangle measure less than 90 degrees, the triangle is an acute triangle.
★ Part B: Fill in the Blank
Write the missing word or number on each line.
1) The corner of a piece of paper forms a right angle that measures 90 degrees.
2) A triangle that contains exactly one 90 degree angle is called a right triangle.
3) When the hour hand points to 12 and the minute hand points to 3, the hands form a right angle.
4) A triangle with one angle measuring 120 degrees must be classified as an obtuse triangle.
★ Part C: Short Answer
Answer each question in one or two complete sentences.
1) How can the corner of a piece of paper help you decide if a triangle has a right angle?
I can place the paper corner against a triangle vertex. If it fits exactly, that angle is 90 degrees, so the triangle is a right triangle.
2) A clock shows 9:00. What kind of angle do the hour and minute hands form, and why?
At 9:00 the hands form a right angle of 90 degrees because the minute hand points to 12 and the hour hand points to 9, making a quarter turn apart.
Ready to Practice?
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9 Questions
15-20 minutes
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