Geometry & MeasuresStudy Notes

Worked Example 3: Co-interior Angles

Part of Angles in Parallel Lines — GCSE Mathematics

This study notes covers Worked Example 3: Co-interior Angles within Angles in Parallel Lines for GCSE Mathematics. Revise Angles in Parallel Lines in Geometry & Measures for GCSE Mathematics with 12 exam-style questions and 3 flashcards. This topic appears less often, but it can still be a useful differentiator on mixed-topic papers. It is section 6 of 8 in this topic. Use this study notes to connect the idea to the wider topic before moving on to questions and flashcards.

Topic position

Section 6 of 8

Practice

12 questions

Recall

3 flashcards

Worked Example 3: Co-interior Angles

Angle a = 72°. Find the co-interior angle b.

Step 1 Recall the rule for co-interior angles

Co-interior angles make a C-shape

Co-interior angles add up to 180°

Step 2 Calculate b

a + b = 180°

72° + b = 180°

b = 180° − 72° = 108°

Reason: Co-interior angles on parallel lines

Practice Questions for Angles in Parallel Lines

Two parallel lines are cut by a transversal. Which statement about alternate angles is correct?

A. Alternate angles add up to 180°
B. Alternate angles are equal
C. Alternate angles add up to 90°
D. Alternate angles are supplementary

1 markfoundation

State the THREE angle rules that apply when a transversal crosses two parallel lines. For each rule, state whether the angles are equal or supplementary.

2 marksstandard

Worked Example 3: Co-interior Angles

Worked Example 3: Co-interior Angles

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Practice Questions for Angles in Parallel Lines

Quick Recall Flashcards

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