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Measuring angles (age 9+)

PROCEDURAL
Mathematics›Geometry|Ages 9—10|ID: mt_89riIKwGYp

Recognise angle measure as additive; find unknown angles by adding or subtracting on a diagram using equations with a symbol for the unknown

Mastery Evidence

  • Two angles on a straight line are 65° and x°; find x = 115°
  • An angle is decomposed into 35° and 40°; state the whole angle is 75°
  • Solve: angles at a point are 120°, 90°, and x°; find x = 150°

Assessment Prompt

“If two angles sit next to each other on a straight line and one is 65°, can [child] work out the other angle — knowing that angles on a straight line always add up to 180°?”

Prerequisites3

Show full prerequisite tree
  • Measuring angles hard

    Must measure angles before solving unknown angle problems

    • Types of angles (age 8+) hard

      Measuring and drawing angles with a protractor requires knowing how to mark and label angles using standard notation

    • Degrees and turns hard

      Using a protractor requires understanding degree measurement

      • What Is an Angle? hard

        Degree measurement system requires understanding what an angle is

        • Types of angles hard

          Angle definition builds on understanding right angles

          • Right Angles & Turns hard

            Identifying right angles and greater/less than right angle is prerequisite to naming acute/obtuse

            • Understanding angles hard

              Identifying right angles requires understanding what an angle is

              • 2-D shapes (age 6+) soft

                Understanding angles as shape properties requires knowing basic shape properties

                • Angles in triangles (age 6+) soft

                  Understanding defining attributes supports describing shape properties formally

                  • 2-D shapes hard

                    Distinguishing defining vs non-defining attributes requires knowing common 2-D shape names first

                  • 3-D shapes (age 5+) hard

                    Identifying defining attributes builds on informal analysis and comparison of shapes

                    • 2-D shapes hard

                      Analysing and comparing shapes requires being able to name them first

                    • 3-D shapes hard

                      Analysing 3-D shapes requires recognising and naming them

                • 2-D shapes hard

                  Describing properties of 2-D shapes (sides, symmetry) requires knowing the shapes first

                • 3-D shapes (age 5+) hard

                  Formal property description extends informal analysis of sides and vertices

                  • 2-D shapes hard

                    Analysing and comparing shapes requires being able to name them first

                  • 3-D shapes hard

                    Analysing 3-D shapes requires recognising and naming them

              • Position, direction, and movement hard

                Recognising angles as turns extends Y2 work on quarter/half/three-quarter turns

            • Types of angles (age 8+) soft

              Identifying right angles and turns is supported by the convention of marking right angles with a small square

            • Position, direction, and movement hard

              Right angles as quarter turns extends Y2 turn vocabulary

              • Positional Language hard

                Position/direction vocabulary with right angles extends basic positional language

              • Turns & Directions hard

                Right-angle turns (clockwise/anti-clockwise) build directly on whole/half/quarter turns from Year 1

        • Right Angles & Turns hard

          Angle definition builds on classifying acute/obtuse angles

          • Understanding angles hard

            Identifying right angles requires understanding what an angle is

            • 2-D shapes (age 6+) soft

              Understanding angles as shape properties requires knowing basic shape properties

              • Angles in triangles (age 6+) soft

                Understanding defining attributes supports describing shape properties formally

                • 2-D shapes hard

                  Distinguishing defining vs non-defining attributes requires knowing common 2-D shape names first

                • 3-D shapes (age 5+) hard

                  Identifying defining attributes builds on informal analysis and comparison of shapes

                  • 2-D shapes hard

                    Analysing and comparing shapes requires being able to name them first

                  • 3-D shapes hard

                    Analysing 3-D shapes requires recognising and naming them

              • 2-D shapes hard

                Describing properties of 2-D shapes (sides, symmetry) requires knowing the shapes first

              • 3-D shapes (age 5+) hard

                Formal property description extends informal analysis of sides and vertices

                • 2-D shapes hard

                  Analysing and comparing shapes requires being able to name them first

                • 3-D shapes hard

                  Analysing 3-D shapes requires recognising and naming them

            • Position, direction, and movement hard

              Recognising angles as turns extends Y2 work on quarter/half/three-quarter turns

              • Positional Language hard

                Position/direction vocabulary with right angles extends basic positional language

              • Turns & Directions hard

                Right-angle turns (clockwise/anti-clockwise) build directly on whole/half/quarter turns from Year 1

          • Types of angles (age 8+) soft

            Identifying right angles and turns is supported by the convention of marking right angles with a small square

          • Position, direction, and movement hard

            Right angles as quarter turns extends Y2 turn vocabulary

            • Positional Language hard

              Position/direction vocabulary with right angles extends basic positional language

            • Turns & Directions hard

              Right-angle turns (clockwise/anti-clockwise) build directly on whole/half/quarter turns from Year 1

              • What Is a Half? soft

                Understanding half and quarter turns benefits from the concept of halves and quarters

                • Division as equal sharing hard

                  Finding a half requires equal sharing into 2 groups — a division concept

                  • Subtraction as taking away or separating hard

                    Division as equal sharing/grouping requires understanding subtraction as taking away/separating

                    • How Many in Total? hard

                      Understanding subtraction as taking away requires knowing numbers represent quantities (cardinality)

                      • One-to-one counting hard

                        Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'

              • Positional Language hard

                Describing movement and turns builds on positional language

  • Types of angles (age 8+) hard

    Finding unknown angles using equations requires reading angle diagrams and interpreting arc marks and notation

  • Angle Sum Rules hard

    Must know angle facts (360°, 180°) to solve unknown angle problems

    • Types of angles (age 8+) hard

      Angle sum rules (360° at a point, 180° on a line) are applied through reading angle diagrams with correct notation

    • Degrees and turns hard

      Angle facts (at a point = 360°) require degree system knowledge

      • What Is an Angle? hard

        Degree measurement system requires understanding what an angle is

        • Types of angles hard

          Angle definition builds on understanding right angles

          • Right Angles & Turns hard

            Identifying right angles and greater/less than right angle is prerequisite to naming acute/obtuse

            • Understanding angles hard

              Identifying right angles requires understanding what an angle is

              • 2-D shapes (age 6+) soft

                Understanding angles as shape properties requires knowing basic shape properties

                • Angles in triangles (age 6+) soft

                  Understanding defining attributes supports describing shape properties formally

                  • 2-D shapes hard

                    Distinguishing defining vs non-defining attributes requires knowing common 2-D shape names first

                  • 3-D shapes (age 5+) hard

                    Identifying defining attributes builds on informal analysis and comparison of shapes

                    • 2-D shapes hard

                      Analysing and comparing shapes requires being able to name them first

                    • 3-D shapes hard

                      Analysing 3-D shapes requires recognising and naming them

                • 2-D shapes hard

                  Describing properties of 2-D shapes (sides, symmetry) requires knowing the shapes first

                • 3-D shapes (age 5+) hard

                  Formal property description extends informal analysis of sides and vertices

                  • 2-D shapes hard

                    Analysing and comparing shapes requires being able to name them first

                  • 3-D shapes hard

                    Analysing 3-D shapes requires recognising and naming them

              • Position, direction, and movement hard

                Recognising angles as turns extends Y2 work on quarter/half/three-quarter turns

            • Types of angles (age 8+) soft

              Identifying right angles and turns is supported by the convention of marking right angles with a small square

            • Position, direction, and movement hard

              Right angles as quarter turns extends Y2 turn vocabulary

              • Positional Language hard

                Position/direction vocabulary with right angles extends basic positional language

              • Turns & Directions hard

                Right-angle turns (clockwise/anti-clockwise) build directly on whole/half/quarter turns from Year 1

        • Right Angles & Turns hard

          Angle definition builds on classifying acute/obtuse angles

          • Understanding angles hard

            Identifying right angles requires understanding what an angle is

            • 2-D shapes (age 6+) soft

              Understanding angles as shape properties requires knowing basic shape properties

              • Angles in triangles (age 6+) soft

                Understanding defining attributes supports describing shape properties formally

                • 2-D shapes hard

                  Distinguishing defining vs non-defining attributes requires knowing common 2-D shape names first

                • 3-D shapes (age 5+) hard

                  Identifying defining attributes builds on informal analysis and comparison of shapes

                  • 2-D shapes hard

                    Analysing and comparing shapes requires being able to name them first

                  • 3-D shapes hard

                    Analysing 3-D shapes requires recognising and naming them

              • 2-D shapes hard

                Describing properties of 2-D shapes (sides, symmetry) requires knowing the shapes first

              • 3-D shapes (age 5+) hard

                Formal property description extends informal analysis of sides and vertices

                • 2-D shapes hard

                  Analysing and comparing shapes requires being able to name them first

                • 3-D shapes hard

                  Analysing 3-D shapes requires recognising and naming them

            • Position, direction, and movement hard

              Recognising angles as turns extends Y2 work on quarter/half/three-quarter turns

              • Positional Language hard

                Position/direction vocabulary with right angles extends basic positional language

              • Turns & Directions hard

                Right-angle turns (clockwise/anti-clockwise) build directly on whole/half/quarter turns from Year 1

          • Types of angles (age 8+) soft

            Identifying right angles and turns is supported by the convention of marking right angles with a small square

          • Position, direction, and movement hard

            Right angles as quarter turns extends Y2 turn vocabulary

            • Positional Language hard

              Position/direction vocabulary with right angles extends basic positional language

            • Turns & Directions hard

              Right-angle turns (clockwise/anti-clockwise) build directly on whole/half/quarter turns from Year 1

              • What Is a Half? soft

                Understanding half and quarter turns benefits from the concept of halves and quarters

                • Division as equal sharing hard

                  Finding a half requires equal sharing into 2 groups — a division concept

                  • Subtraction as taking away or separating hard

                    Division as equal sharing/grouping requires understanding subtraction as taking away/separating

                    • How Many in Total? hard

                      Understanding subtraction as taking away requires knowing numbers represent quantities (cardinality)

                      • One-to-one counting hard

                        Cardinality principle builds on one-to-one correspondence — you must count correctly to know the last number tells 'how many'

              • Positional Language hard

                Describing movement and turns builds on positional language

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