Classifying Acute, Right, Obtuse, Straight, and Reflex Angles

Measuring, Drawing, and Classifying Angles

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Classify angles as acute (<90°), right (90°), obtuse (90°-180°), straight (180°), reflex (180°-360°), or full turns (360°).

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Measuring, Drawing, and Classifying Angles

4th Grade · Math · Open Global Math

8 lessons

Goal

Understand angles as circular turns, measure and construct angles using a protractor and set square, and classify angles from acute to full revolutions.

8 lessons

0 of 8 done

Understanding Angles as Turns and Circular ArcsUp next
Classifying Acute, Right, Obtuse, Straight, and Reflex AnglesYou are here
Recognising That Four Right Angles Make a Complete TurnNot started yet
Using a Protractor to Measure Acute and Obtuse AnglesNot started yet
Measuring Reflex Angles Using ProtractorsNot started yet
Drawing Angles Using a Protractor and RulerNot started yet
Using a Set Square to Construct and Verify Right AnglesNot started yet
Estimating Angle Measures in Real-World ContextsNot started yet

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Learning standards covered

OGM.5.G.2Open Global Math Standards 2026™ · 4th Grade

Recognize angles as geometric turns and circular arc cuts (where a full turn is 360° and 1° is 1/360 of a circle); measure and construct angles using a protractor and set square; classify angles as acute, right (90°), obtuse, straight (180°), reflex, and full revolution (360°); solve additive angle decomposition problems.