Types of Angles

Practise spotting acute, right, obtuse and straight angles — just look at the picture and tap the type.

Grades 4–6 · 4.G⚡ Geometry
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The four types of angles

Angles are sorted by how open they are, compared with a right angle (a square corner, 90°). Learn those four landmarks and you can classify any angle at a glance.

  1. Acute: smaller than a right angle (less than 90°).
  2. Right: exactly 90° — a square corner.
  3. Obtuse: bigger than a right angle but less than a straight line (90°–180°).
  4. Straight: exactly 180° — a straight line.

Worked examples

AcuteAn angle that opens less than a square corner — like 45° — is acute.
ObtuseAn angle wider than a square corner but not yet a straight line — like 130° — is obtuse.
AD AREA (parent reading zone only — never shown during practice)

Tips & common mistakes

The right angle (90°) is your reference point — compare every angle to a square corner. “Acute” angles are small and sharp; “obtuse” ones are wide and blunt. Tap the type shown.

  • Mixing up acute and obtuse — acute is the small, sharp one.
  • Calling a 90° angle acute or obtuse — exactly 90° is right.
  • Judging by the length of the rays instead of how open the angle is.

Frequently asked questions

What are the types of angles?

Acute (less than 90°), right (exactly 90°), obtuse (between 90° and 180°) and straight (exactly 180°).

What is a right angle?

An angle of exactly 90° — a square corner, like the corner of a book or a window.

How do I tell acute from obtuse?

Compare to a square corner. Smaller and sharper is acute; wider and more open is obtuse.

Does the length of the lines matter?

No — only how open the angle is. Long or short rays at the same opening are the same angle.

What grade is this?

Classifying angles is a grade 4 geometry skill, used through grade 6.

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