Identifying features

1.

Use the shapes from page 1 of 2d shapes CM. Place the equilateral triangle card in front of the students.

• What is this shape?
• How do you know it is a triangle?

Students should suggest reasons that refer to either global appearance or features.

• It looks like a mountain/hat/sail.
• It has a bottom and two slopey sides.

Some students may describe properties or relationships between features.

• It has three corners.

2.

Put out these shapes (kite, right-angle triangle, isosceles triangle):

• Are these shapes also triangles?

Let students work in pairs to reach a decision on each shape.

3.

Discuss the criteria for deciding if a shape is a triangle.

• Why is this shape (kite) not a triangle? It has four corners and sides.
• Look for students to say that a triangle has 3 corners and 3 sides.

Consider the two triangles and explicitly address each criterion, pointing to the sides and counting the corners. Be aware that students may be confused by orientation. Turning the cards around so one side is horizontal may help them recognise similarities in the triangles.

4.

Put the three triangles together and label them on a piece of card as "Triangles". Differentiate between the other shapes and the triangle.

• This shape (kite) is not a triangle because it has four corners and four sides.
• Find some other shapes with four corners and four sides.

5.

Lay out the other shape cards for students to select from. Do they choose the shapes below?

6.

• We call a shape with four sides and four corners a quadrilateral. Quad means “four”, and lateral means “side.”
• Are the quadrilaterals the same?
• What differences can you see?

7.

Put the students in pairs and ask them to choose one of the quadrilaterals and describe it. They should record their description for later use. Consider pairing the students to encourage scaffolding, extension, and productive learning conversations.

• Talk about the shape you have.
• Can you describe it to someone else so they can draw your shape?
• Come up with some instructions.

8.

After a suitable time, gather the students. Put all the quadrilaterals into a paper bag so they are hidden.

Provide time for each pair to describe their quadrilateral to the rest of the class. The remaining students should try to draw the shape being described.

Look for students to describe the following features:

• L corners (right angles)
• parallel sides
• side length (longer, shorter, equal)
• turns (rotations)

9.

After students have finished drawing the quadrilateral, pick the shape out of the paper bag and show it to the class.

• Look at the drawings. Do they look like this quadrilateral? How?
• Could you improve your instructions? How?

As students discuss the shapes and instructions given, introduce relevant mathematical vocabulary and te reo Māori kupu (e.g., akitu: vertex, tapa: side/edge) and record them on cards. Encourage students to show what each new term (e.g., akitu: vertex) means in relation to each shape by pointing or gesturing.

6.

Show the remaining three shapes:

1.

Provide the students with opportunities to find the shapes from a figure made of overlapped, transparent shapes.

• Can you find the circle in this picture?
• Can you find the triangle?

Discuss how students might find given shapes in a figure.

• What do you look for?

2.

Use an envelope or piece of paper to partially conceal shapes from pages 1 and 2 of the 2d shapes CM.

• What might this shape be?

As students progress through this activity, encourage them to consider the shapes that have already been revealed as justification for what the concealed shape might be.

This task could be repeated in pairs or small groups.