This Grade 4 worksheet focuses on classifying triangles by side length. Students practice naming equilateral, isosceles, and scalene triangles through correcting sentences, completing fill-in-the-blank items, and writing short answers. The activities reinforce vocabulary like vertex and side while showing how counting equal sides leads to each classification. This Grade 4 worksheet supports classroom practice and homework review at home. Grade 4 students master triangle vocabulary.
Style:
Classifying Triangles
Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1. Fix the sentence:
A triangle with all three sides the same length is called an isosceles triangle.
Rewrite: A triangle with all three sides the same length is called an equilateral triangle.
2. Fix the sentence:
A triangle with no sides the same length is called an equilateral triangle.
Rewrite: A triangle with no sides the same length is called a scalene triangle.
3. Fix the sentence:
An isosceles triangle has three sides of different lengths.
Rewrite: An isosceles triangle has two sides of equal length.
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 equilateral triangle.
2. A triangle with exactly two sides the same length is called an isosceles triangle.
3. A triangle with no sides the same length is called a scalene triangle.
4. Each angle of an equilateral triangle measures 60 degrees.
Part C: Short Answer
Answer each question in one or two complete sentences.
1. How can you classify a triangle by looking only at its side lengths?
Compare the three side lengths. If all three are equal, the triangle is equilateral. If exactly two are equal, it is isosceles. If all three are different, it is scalene.
2. Why is every equilateral triangle also an isosceles triangle in some definitions, but a scalene triangle is never equilateral?
Equilateral triangles have three equal sides, which means they also have at least two equal sides, fitting the isosceles description. Scalene triangles have no equal sides, so they cannot have all three equal.
Classifying Triangles
★ Part A: Fix the Sentence
Each sentence has an error. Rewrite it correctly on the line.
1) Fix the sentence:
A triangle with all three sides the same length is called an isosceles triangle.
Rewrite: A triangle with all three sides the same length is called an equilateral triangle.
2) Fix the sentence:
A triangle with no sides the same length is called an equilateral triangle.
Rewrite: A triangle with no sides the same length is called a scalene triangle.
3) Fix the sentence:
An isosceles triangle has three sides of different lengths.
Rewrite: An isosceles triangle has two sides of equal length.
★ 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 equilateral triangle.
2) A triangle with exactly two sides the same length is called an isosceles triangle.
3) A triangle with no sides the same length is called a scalene triangle.
4) Each angle of an equilateral triangle measures 60 degrees.
★ Part C: Short Answer
Answer each question in one or two complete sentences.
1) How can you classify a triangle by looking only at its side lengths?
Compare the three side lengths. If all three are equal, the triangle is equilateral. If exactly two are equal, it is isosceles. If all three are different, it is scalene.
2) Why is every equilateral triangle also an isosceles triangle in some definitions, but a scalene triangle is never equilateral?
Equilateral triangles have three equal sides, which means they also have at least two equal sides, fitting the isosceles description. Scalene triangles have no equal sides, so they cannot have all three equal.
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9 Questions
15-20 minutes
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