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ISEE Middle Level Quantitative Reasoning · Question of the Day

ISEE Middle Level Quantitative Reasoning Question of the Day

A fresh daily question to build accuracy, reinforce recall, and turn practice into a steady habit.
Monday, August 17, 2026

A triangle has at least two congruent sides and one interior angle of 60°. What is the most specific name for this triangle?

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Question of the Day

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A triangle has at least two congruent sides and one interior angle of 60°. What is the most specific name for this triangle?

  1. Acute isosceles triangle
  2. Right isosceles triangle
  3. Obtuse isosceles triangle
  4. Equilateral triangle (correct answer)

Explanation: If a triangle is isosceles, the angles opposite the congruent sides are equal. Case 1: The 60° angle is the vertex angle. The two base angles are equal and sum to 180°−60°=120°180° - 60° = 120°, so each is 60°. Case 2: The 60° angle is a base angle. The other base angle is also 60°, and the vertex angle is 180°−60°−60°=60°180° - 60° - 60° = 60°. In both cases, all three angles are 60°, which means the triangle is equilateral.