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Angle Names

Recognise acute, obtuse and reflex angles from pictures, diagrams and measures
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This is level 1: Recognise angles in pictures. You will be awarded a trophy if you get at least 7 answers correct and you do this activity online.

1

Angle image

Never smile at a crocodile!

Think of the angle made by its jaws and decide what kind of angle that is.

A crocodile's anatomy allows for a maximum gape of about 75 degrees.

Click one of the buttons below.

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2

Angle image

The angle marked in green in the picture is the angle between the lid of the chest and the top of the chest.

Think what kind of angle that is then click on the green button below.

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3

Angle image

The angle marked in orange is the angle that the screen of a laptop makes with its keyboard when it is fully open.

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4

Angle image

The angle marked on the clock is the larger angle between the two hands.

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5

Angle image

This picture shows the corner of a rectangular garden. The two fences are perpendicular to each other.

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6

Angle image

The angle marked is the outside angle of this pair of compasses.

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7

Angle image

The edges of the pages actually make curved lines but do your best to estimate what kind of angle they will make when they meet at the spine of the book.

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8

Angle image

When you go camping the excitement is intense. Or should that be in tents? Estimate the angle at the apex of this tent.

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9

Angle image

Our paths will cross one day maybe. Estimate the angle marked between these crossing paths.

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10

Angle image

This is the widest these scissors will open. Estimate what kind of angle is marked between the blades.

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Check

Can you correct your mistakes in order to get full marks?

This is Angle Names level 1. You can also try:
Level 2 Level 3

Instructions

Try your best to answer the questions above. Type your answers into the boxes provided leaving no spaces. As you work through the exercise regularly click the "check" button. If you have any wrong answers, do your best to do corrections but if there is anything you don't understand, please ask your teacher for help.

When you have got all of the questions correct you may want to print out this page and paste it into your exercise book. If you keep your work in an ePortfolio you could take a screen shot of your answers and paste that into your Maths file.
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Description of Levels

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Level 1 - Recognise angles in pictures

Level 2 - Estimate the size of angles then name them

Level 3 - Name angles from the number of degrees in the turn

More Angles including lesson Starters, visual aids, investigations and self-marking exercises.

Answers to this exercise are available lower down this page when you are logged in to your Transum account. If you don’t yet have a Transum subscription one can be very quickly set up if you are a teacher, tutor or parent.

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Curriculum Reference

See the National Curriculum page for links to related online activities and resources.

Types of Angle

An angle measures the amount of turn between two rays that meet at a point called the vertex. Angles are measured in degrees (°), and one complete turn all the way round is 360°. Every angle falls into one of these five types according to its size.

e.g. 50°

Acute angle greater than 0° and less than 90°

A sharp, narrow angle — anything smaller than a right angle. Everyday examples include the hands of a clock at 1 o’clock, the point of a slice of pizza, or a pair of scissors that is only slightly open.

90°

Right angle exactly 90°

A quarter of a full turn. It is so common that it has its own symbol — a small square drawn in the corner instead of a curved arc. You will find right angles at the corner of a book, a window, or a sheet of paper.

e.g. 130°

Obtuse angle greater than 90° and less than 180°

Wider than a right angle, but not yet a straight line. Think of a laptop opened well past upright, or the reclined back of a deck chair.

180°

Straight angle exactly 180°

A half turn. The two rays point in exactly opposite directions and together form a straight line. The hands of a clock at 6 o’clock make a straight angle.

e.g. 300°

Reflex angle greater than 180° and less than 360°

Bigger than a straight line but less than a full turn. A reflex angle is the “long way round” — the larger angle you get by measuring the outside of an acute, right or obtuse angle. The wide sweep behind a Pac-Man’s open mouth is a reflex angle.

Quick reference
Type of angleSize
Acute anglegreater than 0° and less than 90°
Right angleexactly 90°
Obtuse anglegreater than 90° and less than 180°
Straight angleexactly 180°
Reflex anglegreater than 180° and less than 360°

Note: an angle of exactly 0° (no turn) and one of exactly 360° (a full turn, also called a complete angle) mark the two ends of the scale. A right angle is neither acute nor obtuse — it sits exactly on the boundary between them, which is why it has a name of its own.

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