Construction of 2D shapes
3rd Maths | Term 1, Unit 1: Geometry
Understanding Properties of 2D Shapes
Let us understand the properties of 2D shapes.
Square
Let us know
A Square has four sides. All the four sides are equal.
Let us make a square by folding a paper by following the given steps.
Step 1: Take a paper
Step 2: Fold the paper as shown in the figure.
Shade the extra portion in the bottom with red colour. Red coloured portion will be rectangular in shape. Tear it off and keep it aside. Open up the triangle. What do you observe? You could see a square.
The crease in the middle of the square is called the 'Diagonal of the square'.
You can note that the diagonal divides the square into two triangles.
Try this
Can you find the other diagonal of the square by folding it the other way? If so how many diagonals can you find for a square?.
Teacher's note:
Teacher can guide the children to do this paper folding activity.
Observe the number of sides and corners of a square.
So, a square has four sides, four corners and two diagonals.
Think
Are all the sides of a square equal
What about the diagonals?
Are they equal?
We know from square shape
we shall summarize the properties of a square as follows
(i) Square has four sides.
(ii) All the four sides are equal.
(iii) Square has four corners.
(iv) Square has two diagonals.
(v) The two diagonals are equal.
Rectangle
Step 1: Take the rectangular piece which was kept aside. Observe its sides.
Let us know:
Opposite sides are equal
Fold the opposite sides of the rectangle. What do you observe? The sides coincide.
Now we get opposite sides equal. Hence in a rectangle, opposite sides are equal.
Fold the opposite corners as we did in the square. Observe the crease. It shows the diagonal of the rectangle.
Let us know:
Diagonals are equal in rectangle.
We know from rectangle shape
The properties of a rectangle are as follows
(i) Rectangle has four sides.
(ii) Two opposite sides are equal.
(iii) Rectangle has four corners.
(iv) Rectangle has two diagonals.
(v) Two diagonals are equal.
Triangle
Fold the square along any of these diagonals to form a triangle.
Observe the Sides and corners of the triangle.
A triangle has three sides and three corners.
Cut the paper and make triangles of different kind.
Observe the length of the sides of the triangle. length of the sides. Let the children explore the names of different sides of the triangles.
Try This:
How many triangles can be made out of this square paper?
Fold the square along any of diagonals to form a triangle.
Let us know
Teacher’s note:
Facilitate the children to explore the properties of shapes in various aspects.
Circle
Let us know:
Circle is a closed curve
Draw a circle using pencil and Bangle.
Step 1: Place a bangle on the paper as shown in figure.
Step 2: Trace the outline of the bangle with a curved line with the pencil until you reach the starting point, we get a circle.
Now, we get a circle
On observing the circle drawn we shall write the properties of it as follows.
(i) Circle has no sides.
(ii) Circle has no corners.
(iii) Circle has a center point.
Activity 1
Write the names of few objects in everyday use and mention their geometrical shapes. Example, table− cuboid
cookies – Circle - Cylinder
wheels of a bike − Circle – Cylinder
ball – sphere
pencil - cylinder
clock faces − Circle
dinner plates − Circle
chess boards − Square
slices of pizza − Triangle
chapter book covers − Rectangle
cell phones – Rectangle - cuboid
Practice
1) Triangle has Three corners.
2) Four sides of a square are Equal.
3) Circle has No sides.
4) Rectangle has Two diagonals.
5) Opposite sides of a rectangle are Equal.
6) Circle has One centre point.
Plane Surface
Surface of few objects like walls, floors papers and top of a table are flat. Flat surfaces are otherwise called as plane surfaces or planes. Cubes and cuboids have flat surfaces.
Curved Surface
Surfaces of few objects such as ball, flowerwase, pot are curved. Cone, Cylinder and sphere have curved surfaces.
Activity 2
Draw all the 2d shapes in the given dot grid. One is done for you.
A geoboard is a mathematical manipulative board.
Join the dots in the grid using curved lines to make designs of your choice. one is done for you.
Teacher’s note :
Teacher can lead the children to make the shapes drawn by them in the dot grid by using rubber band in the Geo board drawn by them in the dot grid
Activity 3
We can see many things around us have straight lines and curved lines.
Draw any 5 shapes and put a tick in the given boxes to indicate the type of the lines found in them.
Teacher’s note :
Teacher can discuss about the types of lines found in objects in everyday use and enable the children to draw them in above tabular column.
Practice
Put a tick mark in the appropriate columns.
