Classifying triangles by angle practice quiz for Grade 5.

📐 Topic Summary

Triangles can be classified based on their angles. An acute triangle has all angles less than 90 degrees. A right triangle has one angle that is exactly 90 degrees. An obtuse triangle has one angle greater than 90 degrees but less than 180 degrees. Understanding these classifications is key to geometry!

🧮 Part A: Vocabulary

Match the terms with their definitions:

Answers:

• 🔍 1 - c
• 💡 2 - a
• 📝 3 - b

✍️ Part B: Fill in the Blanks

Complete the sentences using the words: acute, right, obtuse.

A triangle with angles measuring 60°, 60°, and 60° is an ______ triangle. A triangle with angles measuring 30°, 60°, and 90° is a ______ triangle. A triangle with angles measuring 20°, 40°, and 120° is an ______ triangle.

Answers:

• 🔍 acute
• 💡 right
• 📝 obtuse

🤔 Part C: Critical Thinking

Can a triangle have more than one obtuse angle? Explain why or why not.

Answer:

• 💡 No, a triangle cannot have more than one obtuse angle. The sum of the angles in a triangle must equal 180 degrees. If a triangle had two obtuse angles (each greater than 90 degrees), their sum alone would exceed 180 degrees, which is impossible.