Question

Which property will not be applicable for an equilateral triangle?

• A. All the internal angles of the triangle are equal
• B. All the sides of the triangle are equal
• C. All the external angles are 120° each
• D. All the external angles are 110° each

Hint:

In an equilateral triangle, the external angles are always 120° each.

Answer 1

The Correct Option is D

Step 1: Understanding the Properties of an Equilateral Triangle.
An equilateral triangle has three equal sides and three equal internal angles. Each internal angle measures 60°. The external angles of an equilateral triangle are 120° each (since external angles are supplementary to the internal angles).
Step 2: Verifying the Options.

- Option (1): All the internal angles of an equilateral triangle are equal, and each is 60°.
- Option (2): All sides of an equilateral triangle are equal by definition.
- Option (3): All the external angles are 120° each.
- Option (4): This is incorrect. The external angles of an equilateral triangle are 120°, not 110°. Conclusion:
Therefore, the correct answer is (4) All the external angles are 110° each.