What is an angle?
An angle is formed when two lines meet at a point. We measure angles in degrees (°).
A full turn (spinning all the way around) = 360°
Types of angles
| Type | Degrees | What it looks like |
|---|---|---|
| Acute | Less than 90° | A narrow, sharp angle |
| Right | Exactly 90° | A perfect “L” shape |
| Obtuse | Between 90° and 180° | A wide, open angle |
| Straight | Exactly 180° | A flat line |
Key benchmarks
These angles are worth memorising:
- Quarter turn = 90° (right angle)
- Half turn = 180° (straight angle)
- Three-quarter turn = 270°
- Full turn = 360°
Estimating angles
Use right angles as your reference:
- If it’s smaller than a right angle → acute
- If it’s bigger than a right angle but not flat → obtuse
- You can estimate by thinking “about half a right angle” = about 45°
Angles on a straight line
Angles on a straight line always add up to 180°.
If one angle is 120°, the other must be 180° − 120° = 60°.
Step 1
Step 2
Step 3
Angles on a straight line always sum to 180°. This is one of the most useful angle facts!
Angles at a point
Angles around a full point add up to 360°.
Practice
An angle of 47° is:
47° is less than 90°, so it's an acute angle.
An angle of 135° is:
135° is between 90° and 180°, so it's obtuse.
Two angles sit on a straight line. One angle is 65°. What is the other?
Angles on a straight line add to 180°. 180 − 65 = 115°.
How many degrees is a three-quarter turn?
A full turn is 360°. Three quarters: 360 × 3/4 = 270°.
A clock shows 3 o'clock. What angle do the hands make?
At 3 o'clock, the hands form a quarter turn = 90° (a right angle).
Three angles meet at a point. Two of them are 110° and 85°. What is the third angle?
Angles at a point add to 360°. 360 − 110 − 85 = 165°.
Challenge
Quick-Fire Round