Year 8 · Maths

Understand The Relationship Between Parallel Lines And Angles

3 checked activities 2 video matches

What is the co-interior angle rule?

When a transversal crosses two parallel lines, co-interior angles lie between the parallel lines on the same side of the transversal and add to 180°. If one co-interior angle is 112°, the other is 180° − 112° = 68°. This rule only applies when the two lines are parallel.

Angle rules for parallel lines
Angle pair	Rule	Worked example
Co-interior	Add to 180°	112° + 68° = 180°
Alternate	Are equal	An alternate angle to 68° is 68°
Corresponding	Are equal	A corresponding angle to 112° is 112°

Keep practising: Use the Year 8 Maths checklist

Year 8 learners practise angles in parallel lines alternate and corresponding angles.

The activities include Calculate Angles in Triangles and on Parallel Lines, Find Alternate and Corresponding Angles on Parallel Lines, Find Angles in Triangles and on Parallel Lines. The checked support below includes teach, video, worksheet, teaching. Open a resource in its provider's website and choose the format that best helps the learner explain the idea independently.

Activities covered

Calculate Angles in Triangles and on Parallel Lines
Find Alternate and Corresponding Angles on Parallel Lines
Find Angles in Triangles and on Parallel Lines

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