Mathematics K–6 · Years 1–2

Geoboard shapes: sides, corners and parallel sides

Measurement and space

Practical, model not builtLow risk

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

A two-dimensional shape is classified by its straight sides and corners and by features such as opposite sides that are parallel, not by its size or which way up it sits.

What you need

1 geoboard per pair with a 5 by 5 array of pins (25 pins, 16 small squares)
10 rubber bands per pair
dot paper matching the geoboard
a straight card strip for checking whether sides are parallel

How to do it

Make a triangle, a square, a rectangle that is not a square and a shape with 5 sides. Count the sides and corners of each and copy it onto dot paper.
Make four different four-sided shapes. For each, slide the card strip along one side and across to the opposite side to see whether the two run in the same direction (parallel). Sort the shapes into two pairs parallel, one pair parallel and none.
Turn the geoboard a quarter turn and say whether each shape is still the same kind of shape.
Count every square that can be made on the board: first the 1 by 1 squares, then 2 by 2, 3 by 3 and 4 by 4, then squares that sit on a slant.
With a partner, name one feature two shapes share and one that differs, using the words opposite, parallel, straight and corner.

What you should see

Every shape has as many corners as sides (3 and 3, 4 and 4, 5 and 5). A four-sided shape whose top side is the same length as the bottom side but shifted one pin across has two pairs of parallel sides; one whose top side is shorter than its bottom side and centred over it has one pair. A square turned a quarter turn, or turned onto a corner, is still a square. The board holds 16 + 9 + 4 + 1 = 30 squares with sides along the rows of pins, and 50 squares in all when the slanted squares are counted.

What changes

This activity lists no variables to change, measure and keep the same.

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

A square turned onto its corner is a diamond and no longer a square.
A bigger shape has more corners than a smaller shape of the same kind.

Safety card

Low riskLearners carry it out

Hazards

rubber bands can flick into eyes

Controls

stretch bands close to the board and keep faces back from the pins

Note

No chemicals or heat are used, so the NSW Department of Education Chemical Safety in Schools package is not needed; ordinary classroom supervision under the school's usual risk management.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Mathematics K-10 Syllabus (2022), NSW Education Standards AuthorityMA1-2DS-01 MAO-WM-01
Australian Curriculum v9AC9M2SP01

Sources

The pages the author read to write this activity.

All Concept Studio activities