Q11 of 32 Page 67

In Figure 5.69 which lines are parallel and why?

∠ PAQ + ∠QAB + ∠ PAB = 360° [Angle made on a point = 360°]


55° + ∠ QAB + 255° = 360°


∠ QAB = 360° - 310°


∠ QAB = 50°


Now from the figure,


∠QAB = ∠ABR = 50°


Hence, AQ || BR as alternate interior angles are equal for two parallel lines.


And also ∠RBS = ∠ PAQ = 55°


Hence, PA||BS as alternate angles are equal for two parallel lines.


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