Classifying Triangles Worksheets

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Easy

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Fix the Sentence

Each sentence has an error. Rewrite it correctly on the line.

Part B: Fill in the Blank

Write the missing word or number on each line.

1. A triangle with exactly one 90 degree angle is called a  

2. A triangle in which every angle measures less than 90 degrees is called an  

3. A triangle with one angle that is greater than 90 degrees is called an  

4. The point where two sides of a triangle meet is called a  

Part C: Short Answer

Answer each question in one or two complete sentences.

Classifying Triangles

Easy

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Fix the Sentence

Each sentence has an error. Rewrite it correctly on the line.

Part B: Fill in the Blank

Write the missing word or number on each line.

1. A triangle with all three sides the same length is called an  

2. A triangle with exactly two sides the same length is called an  

3. A triangle with no sides the same length is called a  

4. Each angle of an equilateral triangle measures  

Part C: Short Answer

Answer each question in one or two complete sentences.

Classifying Triangles

Easy

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Fix the Sentence

Each sentence has an error. Rewrite it correctly on the line.

Part B: Fill in the Blank

Write the missing word or number on each line.

1. A traffic yield sign has three congruent sides, so it is an  

2. A pizza slice with two equal long sides and one shorter side is an  

3. A triangle with sides 5 cm, 7 cm, and 9 cm is called a  

4. Each angle inside an equilateral triangle measures  

Part C: Short Answer

Answer each question in one or two complete sentences.

Classifying Triangles

Easy

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Fix the Sentence

Each sentence has an error. Rewrite it correctly on the line.

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  

2. A triangle that contains exactly one 90 degree angle is called a  

3. When the hour hand points to 12 and the minute hand points to 3, the hands form a  

4. A triangle with one angle measuring 120 degrees must be classified as an  

Part C: Short Answer

Answer each question in one or two complete sentences.

Classifying Triangles

Medium

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Fill in the Blank

Write the missing word or number on each line.

1. The three angles of any triangle always add up to  

2. A triangle has angles of 50, 60, and  

3. A triangle has a 90 degree angle and three sides of different lengths. It is a right  

4. Every equilateral triangle is also an  

5. If a triangle has angles of 100, 40, and 40 degrees, it is an obtuse  

6. A right triangle can have its two shorter sides equal in length, making it a right  

7. If two angles of a triangle measure 35 and 55 degrees, the third angle is  

8. A triangle that has all three angles less than 90 degrees is called an  

9. Angles of 70, 70, and 40 degrees describe an  

Part B: Matching

Match each item on the left to the correct answer on the right.

1. Match each item to its correct answer.

Triangle with all sides equal

→

Right triangle

Triangle with one 90 degree angle

→

Equilateral triangle

Triangle with one angle greater than 90 degrees

→

Scalene triangle

Triangle with all three sides different lengths

→

Obtuse triangle

Classifying Triangles

Medium

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Fill in the Blank

Write the missing word or number on each line.

1. A triangle with sides of 5 cm, 5 cm, and 5 cm is called an  

2. A triangle with sides of 7 in, 7 in, and 4 in is called an  

3. A triangle with sides of 3 cm, 4 cm, and 5 cm is called a  

4. If a triangle has angles of 80, 60, and  

5. A right triangle always has exactly  

6. A triangle with angles 110, 35, and 35 degrees is an obtuse  

7. A triangle that is both right and isosceles has angles 90, 45, and  

8. Angles 60, 60, 60 describe an equilateral triangle, which is also an  

9. A triangle with angles of 95, 45, and 40 degrees is an  

Part B: Matching

Match each item on the left to the correct answer on the right.

1. Match each item to its correct answer.

Angles 60, 60, 60

→

Acute scalene

Angles 90, 45, 45

→

Right isosceles

Angles 100, 40, 40

→

Equilateral acute

Angles 80, 60, 40

→

Obtuse isosceles

Classifying Triangles

Medium

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Fill in the Blank

Write the missing word or number on each line.

1. A triangle with three congruent sides and three 60 degree angles is equilateral and  

2. A triangle with two congruent sides and a 90 degree angle is isosceles and  

3. A triangle with three different side lengths and one 110 degree angle is scalene and  

4. A triangle with sides 4, 4, 4 and angles 60, 60, 60 can be classified as equilateral and  

5. A triangle with two equal sides and a 100 degree vertex angle is isosceles and  

6. A triangle with three different sides and three angles of 50, 60, and 70 is scalene and  

7. A triangle with two congruent sides and three angles of 70, 70, and 40 is isosceles and  

8. A triangle with three different sides and a 90 degree angle is scalene and  

9. A triangle with sides 6, 6, 8 and angles 70, 70, 40 is isosceles and  

Part B: Matching

Match each item on the left to the correct answer on the right.

1. Match each item to its correct answer.

Equilateral with all 60 degree angles

→

Equilateral and acute

Isosceles with a 90 degree angle

→

Isosceles and right

Scalene with a 120 degree angle

→

Scalene and obtuse

Scalene with angles 50, 60, 70

→

Scalene and acute

Classifying Triangles

Medium

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Fill in the Blank

Write the missing word or number on each line.

1. If two angles in a triangle measure 60 and 70 degrees, the third angle measures  

2. If two angles in a triangle measure 45 and 45 degrees, the third angle measures  

3. If two angles in a triangle measure 30 and 60 degrees, the third angle measures  

4. A triangle has angles of 80 and 70 degrees. Its third angle measures  

5. If a triangle has angles of 100 and 40 degrees, the third angle measures  

6. A triangle has two angles of 25 and 65 degrees. The third angle measures  

7. If a triangle has angles 110 and 35 degrees, the third angle measures  

8. A triangle has two angles measuring 60 degrees each. The third angle measures  

9. A triangle has angles of 20 and 70 degrees. The third angle measures  

Part B: Matching

Match each item on the left to the correct answer on the right.

1. Match each item to its correct answer.

Two angles 50 and 60

→

Third angle 70 degrees

Two angles 45 and 45

→

Third angle 90 degrees

Two angles 100 and 30

→

Third angle 50 degrees

Two angles 80 and 60

→

Third angle 40 degrees

Classifying Triangles

Hard

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Multiple Choice

Circle the best answer for each question.

1. A triangle has angles of 60 and 70 degrees. What is the third angle?

2. Which set of angles could form a triangle?

3. A triangle has angles of 90, 45, and 45 degrees. How would you classify it?

4. A triangle has sides 6 cm, 6 cm, and 6 cm. Which classification is always correct?

Part B: Fill in the Blank

Write the correct answer on each line.

1. A triangle has angles 35 and 95 degrees. The third angle is  

2. A triangle with angles 30, 60, and 90 degrees is a right  

3. A triangle has angles 20, 20, and  

4. If a triangle has two 50 degree angles, the third angle is  

5. A triangle cannot have two 90 degree angles, because the three angles must add to  

Classifying Triangles

Hard

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Multiple Choice

Circle the best answer for each question.

1. Which triangle is impossible?

2. A triangle has angles 25, 65, and 90 degrees. Classify it.

3. Which set of side lengths describes an isosceles triangle?

4. Two angles of a triangle measure 55 and 55 degrees. What kind of triangle must it be?

Part B: Fill in the Blank

Write the correct answer on each line.

1. A triangle has angles 45, 60, and  

2. A triangle has angles 30, 30, and  

3. A right triangle with two equal legs has angles of 90, 45, and  

4. If a triangle has angles 70, 70, and 40 degrees, it is an acute  

5. A triangle with angles 100, 50, and 30 degrees is an obtuse  

Classifying Triangles

Hard

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Multiple Choice

Circle the best answer for each question.

1. Maya is designing a triangular garden where all three sides must be 8 feet. Which classification fits her garden?

2. Which set of angles cannot form a triangle?

3. A roof truss has two sides of 10 feet and one side of 6 feet. What is its classification by sides?

4. Can a triangle be both right and obtuse at the same time?

Part B: Fill in the Blank

Write the correct answer on each line.

1. If all three sides of a triangular sign are 12 inches, the triangle is classified as  

2. A triangle with sides 5, 5, 5 has angles that each measure  

3. A set of angles 95, 50, and 35 degrees forms a(n)  

4. A triangle cannot have two angles each measuring more than  

5. A triangle with angles 70, 70, and 40 has two equal angles, so its sides also include two  

Classifying Triangles

Hard

Classifying Triangles

Name:

Date:

Grade: Grade 4

Part A: Multiple Choice

Circle the best answer for each question.

1. How many lines of symmetry does an equilateral triangle have?

2. How many lines of symmetry does an isosceles triangle have?

3. How many lines of symmetry does a scalene triangle have?

4. Why does an equilateral triangle have more lines of symmetry than a scalene triangle?

Part B: Fill in the Blank

Write the correct answer on each line.

1. An equilateral triangle has  

2. An isosceles triangle has  

3. A scalene triangle has  

4. A triangle has lines of symmetry only along sides that are  

5. An equilateral triangle's three lines of symmetry each pass through one vertex and the  

Classifying Triangles

What's Included in This Download

What You'll Learn

These classifying triangles worksheets help grade 4 students develop essential math skills through engaging activities.

How to Use These Worksheets

1. Download & Print: Click the download button to get the PDF. Print on standard 8.5" x 11" paper.
2. Start Simple: Begin with easier pages before moving to more challenging activities.
3. Daily Practice: Dedicate 10-15 minutes each day for consistent learning.
4. Use Manipulatives: Pair worksheets with physical objects like blocks or counters.
5. Provide Encouragement: Celebrate progress and effort to build confidence.
6. Check Progress: Use the included answer key to review work together.

Common Mistakes to Watch For

• Mixing up acute and obtuse: acute angles are smaller than 90 degrees, while obtuse angles are larger than 90 degrees.
• Forgetting that the three angles of a triangle must add up to exactly 180 degrees, so two right or two obtuse angles are impossible.
• Confusing equilateral, isosceles, and scalene by counting equal sides incorrectly: equilateral has 3 equal, isosceles has 2 equal, scalene has 0 equal.

Frequently Asked Questions

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