Mathematics
Intermediate
50 mins
Teacher/Student led
+65 XP
What you need:
IWB/Projector/Large Screen

Regular and Irregular Polygons

Learn to identify regular and irregular polygons by comparing side lengths and corners. Explore pentagons, hexagons and octagons, then sort and name them accurately.

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    1 - Getting Started ~4 mins

    Key point

    Every edge on each of these three objects is a straight line.

    Illustration for Getting StartedThe three objects on the board are:

    • a honeycomb cell, with 6 straight edges
    • an octagonal stop sign, with 8 straight edges
    • a six-sided metal nut, with 6 straight edges

    Do all the edges on one object look the same length, or are some longer than others?

    2 - Watch and Notice ~8 mins

    A polygon is a closed flat shape made only of straight sides. Look at the two hexagons on the board. Look at the sides of each one. If every side matches and every corner matches, the shape is regular. If some sides are different lengths, it is irregular.

    Regular means all the sides are equal and all the corners are equal. The last shape is a hexagon that looks a bit odd. Be ready to say what makes it different from the honeycomb hexagon.

    3 - Try It Together ~9 mins

    Key point

    Regular means all sides equal and all corners equal. Irregular means at least one side is different.

    A pentagon has 5 sides, a hexagon has 6 and an octagon has 8. Regular means those sides are all equal.

    Today we sort these polygons together: a pentagon, another pentagon, a hexagon, another hexagon, an octagon, and an octagon that has one short side.

    For each shape, we check every side before we decide.

    Sort by regular or irregular

    4 - Draw Both Hexagons in Your Copy ~3 mins

    COPYBOOK MOMENT

    In your maths copy, draw a regular hexagon and an irregular hexagon side by side. Under them, write one sentence saying how you can tell them apart.

    5 - Class Challenge ~10 mins

    We'll work through four sorts, each a bit harder:

    • clear regular shapes against clearly irregular ones
    • a regular shape turned on its side, so it looks unfamiliar
    • shapes that look regular but have one short side
    • a full mix of pentagons, hexagons and octagons to name and sort

    Regular or irregular: the challenge

    Pupil practice
    Module 7 · 2D and 3D Shapes and Angles Data & Chance
    Lesson 80 · Regular and Irregular Polygons
    Download Activity Book page (PDF)
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