Year 7 · Maths · Lines and angles · Lesson 2
Angle facts: lines, points and crossing lines
Use angles on a straight line, angles around a point and vertically opposite angles to find missing angles, with reasons.
24-minute video lesson
Teaching, worked examples and 20 practice questions solved step by step.
Watch free for a monthWhat your child will learn
- Know angles on a straight line add to 180°
- Know angles around a point add to 360°
- Know vertically opposite angles are equal
- Find missing angles
- Give reasons
The method
- Spot the fact: straight line, point, or crossing lines.
- Write the equation.
- Work out the angle.
- Write the reason in words.
Key words: straight line, point, vertically opposite, angle, reason.
Worked examples
The first three practice questions from the lesson, with every step.
Question 1
Find the size of angle x. Give a reason.
- Step 1: Look at the diagram
- Step 2: Angles on a straight line add up to 180°.
- Step 3: x = 180° − 40° = 140°
Answer: x = 140°
Question 2
Find the size of angle x. Give a reason.
- Step 1: Look at the diagram
- Step 2: Angles on a straight line add up to 180°.
- Step 3: x = 180° − 115° = 65°
Answer: x = 65°
Question 3
Find the size of angle x. Give a reason.
- Step 1: Look at the diagram
- Step 2: Angles on a straight line add up to 180°.
- Step 3: x = 180° − 72° − 38° = 70°
Answer: x = 70°