seegongsik
Grade 1 (age 6-7)

grade 1 2D Shapes

Flat shapes are the thin shapes you can draw on paper: round circles, pointy triangles, and neat squares. A circle has no sides or corners, but a triangle has 3 and a square has 4. Each straight line is a side, and each point where two sides meet is a vertex. Switch shapes and add sides, then count the sides and vertices yourself.

What is a flat shape?

📄 Flat shapes
①These are shapes you can draw on paper
②They are flat, with no thickness
③Let's look at ○, △, and □

Looking at shapes

Circle
🔍 Circle
①A circle is perfectly round
②It has no straight sides and no pointed vertices
③Coins, clocks, and wheels are circles
④It rolls easily in any direction

Counting sides and vertices

3
✏️ Sides and vertices
①Each straight line is a side
②A point where two sides meet is a vertex
③In the picture, the vertices are numbered in order from 1
④A triangle has 3 sides and 3 vertices
⑤A square has 4 sides and 4 vertices
⑥So a shape always has as many vertices as sides

Wrap-up

Circle (○)
0 sides, 0 vertices
Perfectly round, with no pointed corners
Triangle (△)
3 sides, 3 vertices
3 pointed corners and 3 straight lines
Square (□)
4 sides, 4 vertices
4 square corners and 4 straight lines
🎯 Remember
①○ circle: 0 sides, 0 vertices
②△ triangle: 3 sides, 3 vertices
③□ square: 4 sides, 4 vertices
④A rectangle has one pair of sides longer than the other
⑤The number of sides equals the number of vertices

Examples and unit check

Example 1
Which flat shape has 3 sides and 3 vertices?
1
Picture a shape with 3 straight sides.
2
The shape with 3 sides and 3 vertices is a triangle.
▸ A triangle
In a flat shape, the number of sides equals the number of vertices.
Example 2
Which round flat shape has no straight sides and no vertices?
1
Look for a shape with no sides and no vertices at all.
2
A circle has 0 sides and 0 vertices.
▸ A circle
A circle has no straight sides, so it rolls easily in any direction.
Unit check
Which flat shape has 4 sides?
①Triangle
②Square
③Circle
④Point
▸ ② Square
1
Look for the shape with 4 sides and 4 vertices.
2
A triangle has 3 sides and a circle has 0, so the square has 4 sides.
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3D Shapes
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Clock Reading

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