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Class 9 Triangles

Overview

This Class 9 Triangles worksheet builds understanding of triangle types, angle sums, equal sides and angles, and elementary congruence. Use the stated properties to calculate unknown angles and justify each conclusion.

Basic Level Worksheet

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  1. Question 1: How many vertices does a triangle have?
    Solution: A triangle has 3 vertices.
  2. Question 2: What is the sum of the angles in a triangle?
    Solution: The sum of the angles in a triangle is $180^\circ$.
  3. Question 3: A triangle with all three sides equal is called?
    Solution: An equilateral triangle.
  4. Question 4: A triangle with two sides equal is called?
    Solution: An isosceles triangle.
  5. Question 5: A triangle with all three sides of different lengths is called?
    Solution: A scalene triangle.
  6. Question 6: Can a triangle have two right angles?
    Solution: No, because the sum of two right angles is $180^\circ$, which means the third angle would be $0^\circ$.
  7. Question 7: What is the side opposite to the right angle in a right-angled triangle called?
    Solution: It is called the hypotenuse.
  8. Question 8: If two angles of a triangle are $60^\circ$ and $70^\circ$, what is the third angle?
    Solution: The third angle is $180^\circ - (60^\circ + 70^\circ) = 50^\circ$.
  9. Question 9: What does SSS congruence criterion stand for?
    Solution: Side-Side-Side congruence criterion.
  10. Question 10: What does SAS congruence criterion stand for?
    Solution: Side-Angle-Side congruence criterion.
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