With reference to the figure below, consider the two statements:
Statement I: The points A, B, and C will lie on a straight line if x + y = 180∘.
Statement II: If the angle between two lines is 180∘, then all the points on both the lines lie on a straight line.
Both the statements are true and statement 2 is the correct explanation of statement 1
If three or more points lie on same line, they are called collinear points. When the sum of ∠ABD and ∠DBC is equal to 180∘ i.e. x+y= 180∘, (sum of two adjacent angles is 180∘), then they are called as linear pair of angles. Hence the three points lie in the same line and are collinear. So both the statements are true and statement 2 is the correct explanation of statement 1.