Geometry and measuresKS3 / GCSE

Co-interior angles in parallel lines

Use co-interior angles to find missing angle.

  • Check that the lines are marked as parallel.
  • Co-interior angles add to .

Example 1

The marked lines are parallel. Find angle .

Co-interior angles add to 180°.

Example 2

The marked lines are parallel. Find angle .

Co-interior angles add to 180°.

Your turn

Question 1

The marked lines are parallel. Find angle .

Check answer
Co-interior angles add to 180°.
Question 2

The marked lines are parallel. Find angle .

Check answer
Co-interior angles add to 180°.
Question 3

The marked lines are parallel. Find angle .

Check answer
Co-interior angles add to 180°.
Question 4

The marked lines are parallel. Find angle .

Check answer
Co-interior angles add to 180°.
Question 5

The marked lines are parallel. Find angle .

Check answer
Co-interior angles add to 180°.
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