This Grade 4 worksheet combines side and angle classifications and uses the 180 degree angle-sum rule. Students complete fill-in-the-blank problems and a matching set that pairs descriptions with names like right scalene and obtuse isosceles. Hints walk students through subtracting two known angles from 180 to find the missing third angle. This Grade 4 worksheet supports classroom practice and homework review at home.
Style:
Classifying Triangles
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 180 degrees.
2. A triangle has angles of 50, 60, and 70 degrees.
3. A triangle has a 90 degree angle and three sides of different lengths. It is a right scalene triangle.
4. Every equilateral triangle is also an acute triangle, because all its angles are less than 90 degrees.
5. If a triangle has angles of 100, 40, and 40 degrees, it is an obtuse isosceles triangle.
6. A right triangle can have its two shorter sides equal in length, making it a right isosceles triangle.
7. If two angles of a triangle measure 35 and 55 degrees, the third angle is 90 degrees.
8. A triangle that has all three angles less than 90 degrees is called an acute triangle.
9. Angles of 70, 70, and 40 degrees describe an isosceles triangle (by sides) that is also acute.
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
→ Equilateral triangle
Right triangle
Triangle with one 90 degree angle
→ Right triangle
Equilateral triangle
Triangle with one angle greater than 90 degrees
→ Obtuse triangle
Scalene triangle
Triangle with all three sides different lengths
→ Scalene triangle
Obtuse triangle
Classifying Triangles
★ 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 180 degrees.
2) A triangle has angles of 50, 60, and 70 degrees.
3) A triangle has a 90 degree angle and three sides of different lengths. It is a right scalene triangle.
4) Every equilateral triangle is also an acute triangle, because all its angles are less than 90 degrees.
5) If a triangle has angles of 100, 40, and 40 degrees, it is an obtuse isosceles triangle.
6) A right triangle can have its two shorter sides equal in length, making it a right isosceles triangle.
7) If two angles of a triangle measure 35 and 55 degrees, the third angle is 90 degrees.
8) A triangle that has all three angles less than 90 degrees is called an acute triangle.
9) Angles of 70, 70, and 40 degrees describe an isosceles triangle (by sides) that is also acute.
★ 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
→ Equilateral triangle
Right triangle
Triangle with one 90 degree angle
→ Right triangle
Equilateral triangle
Triangle with one angle greater than 90 degrees
→ Obtuse triangle
Scalene triangle
Triangle with all three sides different lengths
→ Scalene triangle
Obtuse triangle
Ready to Practice?
Complete each section carefully.
10 Questions
10-15 minutes
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