This grade 1 shapes lesson explains 2d and 3d shapes in one printable page, with definitions, a method and a worked example.
A shape is described by attributes that stay the same, such as the number of straight sides and corners. A triangle always has 3 sides and 3 corners. Color, size, and the way a shape is turned do not change its name. Shapes can be put together to make new shapes, like two squares making a rectangle.
Grade 1 Shapes Lesson: key facts
- A triangle has 3 straight sides and 3 corners and is closed.
- A square and a rectangle each have 4 sides and 4 square corners.
- Color, size, and turn are not defining attributes.
- A cube, a cylinder, and a cone are 3D shapes.
- Shapes can be put together to make a new shape.
What is a defining attribute?
Every shape has parts we can count. A side is a straight edge. A corner is where two sides meet. A defining attribute is a fact that must be true for a shape to have its name. A triangle always has 3 straight sides and 3 corners, and it is closed with no gaps.
How do you count sides and corners?
Touch each side once and count. Do the same for each corner. Every corner of a triangle sits between 2 sides.
| Shape | Sides | Corners | Defining attribute |
|---|---|---|---|
| Triangle | 3 | 3 | closed, 3 straight sides |
| Square | 4 | 4 | 4 equal sides, 4 square corners |
| Rectangle | 4 | 4 | 4 straight sides, 4 square corners |
| Circle | 0 | 0 | round and closed, no straight sides |
How do you know a shape is not a triangle?
Check the attributes. If a shape has a gap, it is open, so it is not a triangle. If it has 4 sides, it is not a triangle. A circle has no straight sides at all.
What are the 3D shapes?
A cube is shaped like a number cube. All of its flat sides are squares. A cylinder is shaped like a can. It has two flat circles. A cone has one flat circle and a pointed top. A box looks like a cereal box.
How do you put shapes together?
Slide the shapes so they touch. Do not let them overlap. Then name the new shape and count the pieces.
- Choose the shapes.
- Slide them together along a side.
- Name the new shape.
- Count the pieces.
Example. Two squares of the same size touch along one side. They make a rectangle. Two triangles of the same size can make a square.
You can stack 3D shapes too. A tower of 3 cubes next to a tower of 2 cubes uses \(3 + 2 = 5\) cubes.
2D and 3D Shapes: frequently asked questions
What is a defining attribute?
A defining attribute is a fact that must be true for a shape to have its name. A triangle must be closed and have 3 straight sides. Color and size are not defining.
What is the difference between a square and a rectangle?
Both have 4 sides and 4 square corners. A square has 4 sides that are all the same length. A rectangle can have long sides and short sides.
Is a turned triangle still a triangle?
Yes. Turning a shape does not change its sides or corners. A triangle that points down is still a triangle.
What shape does a can of soup look like?
A can of soup looks like a cylinder. A cylinder has two flat circles, one on the top and one on the bottom.
How can you make a rectangle from other shapes?
Slide two squares of the same size together along one side. The new shape is a rectangle. You can also use two rectangles.
How to use this grade 1 shapes lesson
Use this grade 1 shapes lesson before the worksheet, then check what you learned with the quiz.
See every chapter on the Grade 1 math page.