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A teacher in Pune says: 'If the two interior angles on the same side of a transversal are unequal but still add up to 180°, the two lines are not parallel.'
Is the teacher's claim correct?

Class 9The Fifth PostulateGeometry — Foundations
  • ANo; if the sum is 180° the lines are parallel regardless of being unequal
  • BYes; only equal angles give parallel lines
  • CYes; unequal angles always meet
  • DCannot be decided

Step-by-Step Solution

The fifth postulate depends only on the SUM of the co-interior angles. If the sum is exactly 180°, the lines are parallel even if the two angles are unequal (e.g. 70 and 110).
Answer: A) No; if the sum is 180° the lines are parallel regardless of being unequal

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