Less than a right angle
A small turn can be less than a right angle.
smaller opening
Compare it with a quarter turn.
Year 3
Identify whether angles are greater than or less than a right angle
Compare an angle to a right angle and say whether it is smaller or larger.
Lesson overview
Geometry - properties of shape
A right angle gives us a useful benchmark. If an angle opens less than a right angle, it is smaller than a right angle. If it opens more, it is greater than a right angle.
A right angle benchmark
A quarter turn makes a right angle.
benchmark
Use this size to compare other angles.
Greater than a right angle
A wider opening can be greater than a right angle.
wider than a quarter turn
It is wider than the right angle benchmark.
Worked example
An angle opens wider than a quarter turn but less than a half turn. Is it greater or less than a right angle?
compare with a right angle
- A right angle is one quarter turn.
- This angle opens wider than a quarter turn.
- That means it is larger than a right angle.
- So it is greater than a right angle.
Try it
Picture a right angle first, then decide whether the angle opens less or more than that.
Question 1
An angle smaller than a right angle is...
less than right angle
Question 2
An angle wider than a right angle is...
greater than right angle
Question 3
Which angle matches a right angle?
quarter turn
Question 4
How many degrees are in the right angle turn shown here? Write the number only.
90 degrees
Question 5
Which statement is correct?
Common mistakes
Watch for these when working through the lesson.
- Judging the angle by line length instead of opening size.
- Forgetting what a right angle looks like.
- Thinking all wide angles are half turns.
Related topics
These ideas fit closely with this lesson.
- Identify right angles and recognise that two make a half-turn, three make three quarters of a turn and four make a complete turn.
- Identify horizontal and vertical lines and pairs of perpendicular and parallel lines.