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Grade 3 (age 8-9)

Plane Figures

Plane Figures

Look around and you will spot shapes everywhere, like triangular signs, rectangular blackboards, and round clocks. Every figure is made of vertices, sides, and angles, and counting them tells you whether it is a triangle or a quadrilateral. A square has four equal sides, a rectangle has equal opposite sides, and a circle has no sides or vertices at all. On this page you can switch between shapes with the buttons and change their size to see how the sides and vertices change.

What is a Shape?
📐 Shapes Around Us
①The classroom blackboard is a rectangle
②A clock is a circle
③Triangles in road signs
④Shapes are made of points, lines, and faces
Let's Look at Shapes
10
💡 Parts of a Shape
①Vertex: where sides meet
②Side: line connecting vertices
③Angle: gap between two meeting sides
④Circle has no vertices/sides — has center and radius
Summary
Triangle
3 vertices + 3 sides + 3 angles
Surrounded by 3 straight lines
Quadrilateral
4 vertices + 4 sides + 4 angles
Surrounded by 4 straight lines
Circle
Set of points at equal distance (radius) from center
Round shape with no vertices or sides
🎯 Key Points
①Triangle: 3 sides, 3 vertices
②Quad: 4 sides, 4 vertices
③Square has 4 equal sides and right angles
④Rectangle has equal opposite sides and right angles
⑤Circle has no sides/vertices, equal distance from center
Examples and Unit Test
Example 1
What is the name of a shape with 3 sides, 3 vertices, and 3 angles?
1
Tell shapes apart by their number of sides, vertices, and angles.
2
A shape with 3 sides, 3 vertices, and 3 angles is a triangle.
▸ Triangle
In one shape, the number of sides, vertices, and angles are all equal.
Example 2
What is the name of a quadrilateral with 4 equal sides and 4 right angles?
1
A quadrilateral has 4 sides and 4 vertices.
2
The one with all 4 sides equal and all 4 angles right is a square.
▸ Square
A rectangle has only opposite sides equal, but a square has all 4 sides equal.
Unit Test
Which shape has no vertices or sides and is at equal distance from a center?
①triangle
②rectangle
③circle
④square
▸ ③ circle
1
A circle has no straight sides and no vertices.
2
A circle is the set of points at equal distance (radius) from a center.
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Fractions
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