Chapter 6: Lines and Angles

Overview

This Class 9 Lines and Angles worksheet practises angle relationships formed by intersecting and parallel lines, transversals, and angle sums in triangles. Use the given ratios and angle facts to show each calculation clearly.

Basic Level Worksheet

  1. Question 1: What is the sum of the angles in a linear pair?
    Solution: The sum of angles in a linear pair is $180^\circ$.
  2. Question 2: Find the complement of an angle of $65^\circ$.
    Solution: Complement $= 90^\circ - 65^\circ = 25^\circ$.
  3. Question 3: If two lines intersect each other, what is the relation between vertically opposite angles?
    Solution: Vertically opposite angles are equal.
  4. Question 4: An angle is greater than $90^\circ$ and less than $180^\circ$. What type of angle is it?
    Solution: It is an Obtuse angle.
  5. Question 5: In $\triangle ABC$, if $\angle A = 50^\circ$ and $\angle B = 60^\circ$, find $\angle C$.
    Solution: $\angle A + \angle B + \angle C = 180^\circ$ (Angle sum property).
    $50^\circ + 60^\circ + \angle C = 180^\circ \Rightarrow 110^\circ + \angle C = 180^\circ \Rightarrow \angle C = 70^\circ$.
  6. Question 6: Find the supplement of $110^\circ$.
    Solution: Supplement $= 180^\circ - 110^\circ = 70^\circ$.
  7. Question 7: If a transversal intersects two parallel lines, then consecutive interior angles are?
    Solution: Consecutive interior angles (or co-interior angles) are supplementary (sum is $180^\circ$).
  8. Question 8: What is the measure of a complete angle?
    Solution: A complete angle measures $360^\circ$.
  9. Question 9: Can a triangle have two right angles?
    Solution: No, because the sum of two right angles is $180^\circ$, leaving $0^\circ$ for the third angle, which is not possible.
  10. Question 10: If one angle of a linear pair is acute, then what kind of angle is the other?
    Solution: The other angle must be obtuse (since sum is $180^\circ$).
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