Students complete nine sentences about regular polygon properties, isosceles triangles with unequal third sides, and acute angle counts. The matching activity pairs three equal sides, one 90° angle, no equal sides, and two equal sides with their triangle classifications.
Matching triangle descriptions to their classification names consolidates both the sides-based and angles-based classification systems into a single four-way reference, covering equilateral, right, scalene, and isosceles.
Style:
Classifying 2D Shapes
Part A: Fill in the Blank
Write the missing word or number on each line.
1. A regular polygon has all sides equal and all angles equal.
2. A triangle with sides 5 cm, 5 cm, and 8 cm is classified as isosceles.
3. An acute triangle has 3 angles that are each less than 90°.
4. A triangle with angles 30°, 60°, and 90° is classified as a right triangle.
5. The third angle of a triangle with two angles of 45° each measures 90 degrees.
6. A triangle with sides 3 cm, 4 cm, and 5 cm is a scalene triangle by its sides.
7. An equilateral triangle has three angles that each measure 60 degrees.
8. A pentagon is a polygon with 5 sides.
9. A triangle with one angle of 120° is called a(n) obtuse triangle.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Three equal sides, all angles 60°
→ Equilateral triangle
Isosceles triangle
One angle exactly 90°
→ Right triangle
Equilateral triangle
No equal sides, no equal angles
→ Scalene triangle
Scalene triangle
Two equal sides, two equal base angles
→ Isosceles triangle
Right triangle
Classifying 2D Shapes
★ Part A: Fill in the Blank
Write the missing word or number on each line.
1) A regular polygon has all sides equal and all angles equal.
2) A triangle with sides 5 cm, 5 cm, and 8 cm is classified as isosceles.
3) An acute triangle has 3 angles that are each less than 90°.
4) A triangle with angles 30°, 60°, and 90° is classified as a right triangle.
5) The third angle of a triangle with two angles of 45° each measures 90 degrees.
6) A triangle with sides 3 cm, 4 cm, and 5 cm is a scalene triangle by its sides.
7) An equilateral triangle has three angles that each measure 60 degrees.
8) A pentagon is a polygon with 5 sides.
9) A triangle with one angle of 120° is called a(n) obtuse triangle.
★ Part B: Matching
Match each item on the left to the correct answer on the right.
1) Match each item to its correct answer.
Three equal sides, all angles 60°
→ Equilateral triangle
Isosceles triangle
One angle exactly 90°
→ Right triangle
Equilateral triangle
No equal sides, no equal angles
→ Scalene triangle
Scalene triangle
Two equal sides, two equal base angles
→ Isosceles triangle
Right triangle
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10 Questions
10-15 minutes
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