Stage 1 - space and geometry – 2D
- name and describe common 2D shapes
- identify parallel lines
Activities to support the strategy
Activity 1: 2D shapes and parallel lines
1. Collect a variety of transparent coloured plastic 2D shapes, such as rectangles, squares, rhombuses, hexagons and trapeziums. The teacher:
- displays the 2D shapes on a whiteboard or overhead projector and models the pronunciation of shape names while showing flashcards of names
- asks students to match the name cards to the shapes which are displayed
- moves the labels to the bottom of the whiteboard (modify for overhead projector). Teacher and students name each shape and students match labels to shapes
- removes one shape at a time while students have their eyes closed. The students have to draw the missing shape and copy the label from the board.
Students select a 2D shape and describe the shape to the class.
Students are given a 2D shape and find other students who have shapes with similar properties. They then explain what the properties were that grouped them together, for example:
- We all have shapes with three sides.
- We all have shapes with curved edges.
2. Students are given a variety of pattern blocks. Discuss the features of each block and count the number of sides and corners.
Use the pattern blocks to make other shapes by joining. The teacher models the mathematical language while the students discuss the features of the shapes they are constructing, e.g. Ellie has made a shape with all the sides equal and all corners equal.
3. The teacher collects or constructs a variety of 2D shapes (pattern blocks, transparent plastic shapes) to use with an IWB/camera projector and leads the following class activity as a discussion.
- Place two identical equilateral triangles on the projector.
- Join the two triangles together to make a new shape.
Ask: What shape have I made?
- Place two identical isosceles triangles on the projector.
Ask: What shape do you think I can make if these two triangles are joined? Students give reasons to justify their answer.
- Repeat with two trapeziums.
Students use the pattern blocks to make other 2D shapes or pictures by joining. Students describe their pictures and the shapes they used to make them and display the pictures.
4. Ask students to find the number of rectangles in the diagram below and explain or write how they know they have found all of the rectangles.
5. Students make a list of parallel lines in the classroom. Ask students to explain what makes the lines parallel.
The teacher displays pictures of the environment which include parallel lines. Point to different pairs of lines in the pictures and ask students if the lines are parallel.
6. Students label shapes on a worksheet and identify the parallel lines. Vary the orientation of the shapes (see example below).
Activity 2: symmetry
1. Students are given a worksheet with a variety of 2D shapes. They cut out each shape and fold it exactly in half in as many ways as they can.
- Which shapes can be folded in half only once?
- Which shapes can be folded in half in more than one way?
- When two halves exactly overlap, what is the line along the fold called?
- On each of the cut outs, students draw the line of symmetry along each fold line.
Students complete the table to record whether each of the shapes is symmetrical and indicate how many lines of symmetry each shape has.
Students discuss the information. Compare the shapes with the same number of sides. Ask questions such as:
- Do all four-sided shapes have the same number of lines of symmetry?
- Do all five-sided shapes have the same number of lines of symmetry?
2.Students trace around a circular container and cut out the circle. They
- fold the circle in half once
- fold it in half twice
- then fold it again and again and again.
- How many times can you fold a circle exactly in half?
- Can you count the number of times?
Have students explain how many lines of symmetry they think a circle has.
ACMMG042 Describe and draw two-dimensional shapes, with and without digital technologies
MA1-15MG Manipulates, sorts, represents, describes and explores two-dimensional shapes, including quadrilaterals, pentagons, hexagons and octagons
- Developing Efficient Numeracy Strategies: Stage 2, NSW Department of Education and Training, pp. 228-229, 308-309, 314-315
- Homeschoolmath.net – line symmetry
- Pattern Blocks: Virtual pattern blocks include: triangles, squares, rhombi, trapezoids, hexagons and chevrons.