New
New
Year 8

# Angles on parallel lines traversed by a straight line

I can use facts about a pair of parallel lines traversed by a straight line.

New
New
Year 8

# Angles on parallel lines traversed by a straight line

I can use facts about a pair of parallel lines traversed by a straight line.

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## Lesson details

### Key learning points

1. Alternate, corresponding and co-interior angles can be identified in diagrams containing pairs of parallel lines.
2. Facts about angles in parallel lines can be used to find unknown angles.
3. Facts about angles in parallel lines can be used in succession to find multiple unknown angles.

### Common misconception

Pupils may struggle with the justifications rather than getting to the answer.

Keep asking pupils "why?" and encourage them to ask themselves, whenever they are working out an angle.

### Keywords

• Parallel - Two lines are parallel if they are straight lines that are always the same (non-zero) distance apart.

• Alternate angles - a pair of angles both between or both outside two line segments that are on opposite sides of the transversal that cuts them.

• Corresponding angles - Corresponding angles are a pair of angles at different vertices on the same side of a transversal in equivalent positions.

• Co-interior angles - o-interior angles are on the same side of the transversal line and in between the two other lines.

• Vertically opposite angles - Vertical angles are pairs of opposite angles formed when two lines intersect at a point. They are equal.

Pupils could make their own parallel line problem up for peers to complete. They can think about how many angles are necessary to give and the most efficient route to the answer.
Teacher tip

### Licence

This content is © Oak National Academy Limited (2023), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Starter quiz

### 6 Questions

Q1.
Using this diagram, you know that the angles are supplementary so \$\$a\$\$ is °.
Q2.
Which of these show equal angles?
Q3.
Which of these pairs of angles are equal corresponding angles?
\$\$a\$\$ and \$\$h\$\$
\$\$d\$\$ and \$\$e\$\$
\$\$g\$\$ and \$\$h\$\$
Q4.
is marked with the letter \$\$a\$\$.
Q5.
Which of the following are always true statements about the angles marked \$\$x\$\$ and \$\$y\$\$?
\$\$x=y+180\$\$
\$\$y=x+180\$\$
\$\$x=y\$\$
Q6.
\$\$3x+14=7x-46\$\$ as the angles are equal angles.

## Exit quiz

### 6 Questions

Q1.
Two lines are parallel if they are straight lines that are always the same (non-zero) apart.
Q2.
For the two lines crossing the transversal to be parallel, if \$\$c=100°\$\$ then \$\$g=\$\$ °.
Q3.
Which statement about the diagram is correct?
Correct answer: \$\$x° = 126°\$\$ as the angles are equal interior alternate angles
\$\$x° = 126°\$\$ as the angles are equal exterior alternate angles
\$\$x° = 126°\$\$ as the angles are equal corresponding angles
Q4.
Which single additional parallel line is needed on the diagram to enable you to find the value of \$\$x\$\$?
a