Shapes, Angles, Perimeter and Area
Year 8 Mathematics Properties of Geometrical Figures Perimeter and Area Calculations
WALT - We Are Learning To
Identify and classify triangles, quadrilaterals, and polygons Calculate angle sums for different shapes Find perimeter and area of various geometric figures Convert between units of length and area Apply inverse operations to solve for unknown measurements
Success Criteria
I can name and draw different types of triangles and quadrilaterals I can calculate missing angles using angle sum rules I can find perimeter and area using appropriate formulas I can convert between mm, cm, m, and km for length I can convert between mm², cm², m², and km² for area I can rearrange formulas to find missing side lengths or heights
What shapes can you see around our classroom?
Look around and identify geometric shapes Think about 2D and 3D shapes Consider angles and parallel lines
Triangle Review - Consolidating Knowledge
Equilateral: all sides equal, all angles 60° Isosceles: two sides equal, two angles equal Scalene: all sides different, all angles different Right-angled: one angle is 90° Angle sum rule: angles in a triangle add to 180°
Triangle Classification Activity
Measure the sides and angles of given triangles Classify each triangle by sides AND angles Use rulers and protractors accurately Record measurements in a table
Quadrilaterals - New Territory
Square: 4 equal sides, 4 right angles Rectangle: opposite sides equal, 4 right angles Parallelogram: opposite sides parallel and equal Rhombus: 4 equal sides, opposite angles equal Trapezium: one pair of parallel sides Kite: two pairs of adjacent equal sides
Quadrilateral Properties Comparison
{"left":"Regular Quadrilaterals: Square (all sides equal, all angles 90°), Rhombus (all sides equal, opposite angles equal)","right":"Irregular Quadrilaterals: Rectangle (opposite sides equal, all angles 90°), Parallelogram (opposite sides parallel and equal), Trapezium (one pair parallel sides), Kite (two pairs adjacent equal sides)"}
Angle Sums in Quadrilaterals
All quadrilaterals have angle sum of 360° Can be proven by dividing into two triangles Each triangle contributes 180° Therefore: 180° + 180° = 360° This works for ANY quadrilateral shape
Find the Missing Angles
Use the 360° rule for quadrilaterals Set up equations to solve for unknown angles Check your answers by adding all four angles Try increasingly challenging problems
Polygons - Extending Our Knowledge
Pentagon: 5 sides, angle sum = 540° Hexagon: 6 sides, angle sum = 720° Octagon: 8 sides, angle sum = 1080° General formula: (n-2) × 180° Where n = number of sides
Challenge: What's the angle sum of a 12-sided polygon?
Use the formula (n-2) × 180° Show your working clearly Think about how to check your answer
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