Skip to main content

Maths · Geometry

Classify an angle

Classify one angle by size or compare it with a reference turn.

Free to use and free to share. There is no sign-up, no score, and nothing a child does here is recorded or sent anywhere.

Practise it now

The size of the marked angle is written on it. Which word names that angle?

Loading the interactive exercise. Nothing you do here is saved or scored.

A worked example

One question of the kind this skill is tested with, worked all the way through: the reasoning, and what the wrong answers are there to catch.

Naming an angle by its size

Which word describes angle C?

Angle C of this quadrilateral is marked with its size.

  1. obtuse
  2. right
  3. acute

Answer: acute

How you get there

Angle C measures 84°, and any angle smaller than a right angle is acute.

Why the other answers tempt

A long pair of sides does not make a bigger angle - only how far the corner opens counts.

If they are stuck, say this

Compare the angle with a right angle of 90° and with a straight line of 180°, and see which side of each it falls.

Now do it live in Angle Namer

What this exercise is doing

Angle Namer

The size of the marked angle is written on it. Which word names that angle?

The angle opens 177°, which is past the quarter turn of 90° but has not reached the straight line of 180°, so it is obtuse.

What to say if they get stuck

  1. Hold the corner against a quarter turn. Does it open less far than a square corner, or further?
  2. A straight line is 180°, which is two square corners side by side. Anything smaller than one square corner is acute.
  3. Put the printed size next to 90 and next to 180, and see which side of each it falls on.

Open Angle Namer on its own page to share it

Related maths skills

All maths 11+ skills

Questions parents ask about classify an angle

Answered from what the skill map records about this skill, not from a template. Every answer here is on the page, and the same questions are the page's FAQ structured data.

Classify one angle by size or compare it with a reference turn. It is one of 55 named maths skills in the 11+, in the geometry strand, and this page carries 1 interactive exercise that practises it.

Knowing which maths topic to practise is most of the work

A free diagnostic covers arithmetic, fractions, geometry, measure and data handling, and comes back with the topics to spend the next few weeks on.