AC9M6M04Year 6MeasurementPractised on site

AC9M6M04 — Year 6 Measurement

Official Curriculum Content Description:

identify the relationships between angles on a straight line, angles at a point and vertically opposite angles; use these to determine unknown angles, communicating reasoning

Worked Examples (3)

Example 1Angles Meeting at a Point
Angles around a point add up to 360°. Given angles of 55°, 80° and 90° around a point, find the size of angle xx.
Common mistake: Subtracted from 180° instead of 360°
Correct Answer:135°135°
Accepted: A unit is optional (degrees, deg, ° all accepted).
Worked Solution:
Angles around a point add up to 360°. Known total = 225°, so x = 360° − 225° = 135°.
Example 2Vertically Opposite Angle Calculations
In the diagram of intersecting lines below, given angle 65∘65^\circ, find the vertically opposite angle xx.
65°x
Diagram not accurately drawn
Common mistake: Added the angles instead of setting them equal
Correct Answer:65°65°
Accepted: A unit is optional (degrees, deg, ° all accepted).
Worked Solution:
Vertically opposite angles are equal. So x = 65°.
Example 3Supplementary Angles on a Straight Line
On the straight line below, given angle 121∘121^\circ, find the size of angle xx.
121°x
Diagram not accurately drawn
Common mistake: Subtracted from 90° instead of 180°
Correct Answer:59°59°
Accepted: A unit is optional (degrees, deg, ° all accepted).
Worked Solution:
Angles on a straight line add up to 180°. So x = 180° − 121° = 59°.

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