Solving Problems, SM-Bank 007

Determine if two lines in the diagram below are parallel, giving reasons for your answer. (2 marks)

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\(\angle \text{unknown} = 360-310=50^{\circ}\ \ \text{(360° about a point)}\)

\(\text{Since cointerior angles sum to 180°:}\)

\(140 + 50= 190^{\circ} \neq 180^{\circ}\)

\(\therefore \ \text{Lines are not parallel.}\)

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\(\angle \text{unknown} = 360-310=50^{\circ}\ \ \text{(360° about a point)}\)

\(\text{Since cointerior angles sum to 180°:}\)

\(140 + 50 = 190^{\circ} \neq 180^{\circ}\)

\(\therefore \ \text{Lines are not parallel.}\)