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Classifying triangles

Use side lengths to name equilateral, isosceles and scalene triangles.

Practice + answer key · 4 pages

Worksheet settings8 questions · 2 columns · A4
Side lengths

All three sides stay in this range. A wider range allows more side classifications.

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mathsprig-1
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643c0c78
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2 pages
Classifying trianglesClassifying triangles. Practice. Classify this triangle by its side lengths. Classify this triangle by its side lengths. Classify this triangle by its side lengths. Classify this triangle by its side lengths.Name __________________________Date _______________Classifying trianglesClassify each triangle by its sides.Worked exampleA triangle has side lengths 5 cm, 5 cm, and 8 cm. → IsoscelesTwo sides are 5 cm, while the third is 8 cm.1.Classify this triangle by itsside lengths.Triangle with side lengths 3 cm, 8 cm, and 8 cm.3 cm8 cm8 cm2.Classify this triangle by itsside lengths.Triangle with side lengths 3 cm, 4 cm, and 5 cm.3 cm4 cm5 cm3.Classify this triangle by itsside lengths.Triangle with side lengths 3 cm, 6 cm, and 6 cm.3 cm6 cm6 cm4.Classify this triangle by itsside lengths.Triangle with side lengths 3 cm, 3 cm, and 3 cm.3 cm3 cm3 cmMathSprig · mathsprig.site · support@mathsprig.sitePage 1 of 2mathsprig-1 · mathsprig-v1 · 643c0c78
Classifying trianglesClassifying triangles. Practice. Classify this triangle by its side lengths. Classify this triangle by its side lengths. Classify this triangle by its side lengths. Classify this triangle by its side lengths.Name __________________________Date _______________Classifying trianglesClassify each triangle by its sides.5.Classify this triangle by itsside lengths.Triangle with side lengths 6 cm, 7 cm, and 8 cm.6 cm7 cm8 cm6.Classify this triangle by itsside lengths.Triangle with side lengths 3 cm, 3 cm, and 3 cm.3 cm3 cm3 cm7.Classify this triangle by itsside lengths.Triangle with side lengths 3 cm, 4 cm, and 4 cm.3 cm4 cm4 cm8.Classify this triangle by itsside lengths.Triangle with side lengths 6 cm, 6 cm, and 6 cm.6 cm6 cm6 cmMathSprig · mathsprig.site · support@mathsprig.sitePage 2 of 2mathsprig-1 · mathsprig-v1 · 643c0c78
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Practice + answer key · 4 pages

Geometry

What you’ll practice

Classify a triangle by its side lengths.

Read all three side lengths. Three equal sides make an equilateral triangle; exactly two equal sides make an isosceles triangle on this sheet.

How this skill works

An equilateral triangle has three equal sides. An isosceles triangle here means exactly two equal sides.

A scalene triangle has no equal sides. Every generated triangle satisfies the triangle inequality, so its shorter sides together exceed the longest.

Worked example

A triangle has side lengths 5 cm, 5 cm, and 8 cm.
  1. Two sides are 5 cm, while the third is 8 cm.
  2. Exactly two sides are equal, so this is an isosceles triangle.

Answer: Isosceles

Teaching notes

  • Use the side labels; do not judge equality from a quick glance.
Practice questions
  1. Classify this triangle by its side lengths.

    Triangle with side lengths 3 cm, 8 cm, and 8 cm.

  2. Classify this triangle by its side lengths.

    Triangle with side lengths 3 cm, 4 cm, and 5 cm.

  3. Classify this triangle by its side lengths.

    Triangle with side lengths 3 cm, 6 cm, and 6 cm.

  4. Classify this triangle by its side lengths.

    Triangle with side lengths 3 cm, 3 cm, and 3 cm.

  5. Classify this triangle by its side lengths.

    Triangle with side lengths 6 cm, 7 cm, and 8 cm.

  6. Classify this triangle by its side lengths.

    Triangle with side lengths 3 cm, 3 cm, and 3 cm.

  7. Classify this triangle by its side lengths.

    Triangle with side lengths 3 cm, 4 cm, and 4 cm.

  8. Classify this triangle by its side lengths.

    Triangle with side lengths 6 cm, 6 cm, and 6 cm.

Answers and steps
  1. Isosceles
    1. Exactly two sides are equal, so the triangle is isosceles.
  2. Scalene
    1. The side lengths 3, 4, and 5 cm are all different, so the triangle is scalene.
  3. Isosceles
    1. Exactly two sides are equal, so the triangle is isosceles.
  4. Equilateral
    1. All three sides are 3 cm, so the triangle is equilateral.
  5. Scalene
    1. The side lengths 6, 7, and 8 cm are all different, so the triangle is scalene.
  6. Equilateral
    1. All three sides are 3 cm, so the triangle is equilateral.
  7. Isosceles
    1. Exactly two sides are equal, so the triangle is isosceles.
  8. Equilateral
    1. All three sides are 6 cm, so the triangle is equilateral.