Thursday, 23 October 2014

An Open Sort dealing with Similarity and Congruence

In this activity students are given a card that has some sort of image on it. This is an open sort. That is students are then asked to sort themselves with no other instructions. Teachers are often leery of this type activity (with so few instructions) because they are worried that it might not go the way they want. Sometimes that is true but most times kids will do alright. And they need opportunities to think freely about math without the burden of assessment. This is a great way to do it.
New: Alternatively, you could have students just work individually on this Desmos card sort


  • Gr7GS - distinguish between and compare similar shapes and congruent shapes, using a variety of tools
  • Gr8GS - determine, through investigation using a variety of tools (e.g., dynamic geometry software, concrete materials, geoboard), relationships among area, perimeter, corresponding side lengths, and corresponding angles of similar shapes.
Set of Open Sort cards. There are 21 all together so you may need two sets if you have a bigger class. Print them on card stock, cut them out and laminate (optional)


  1. Each student is given a card 
  2. Ask students to sort themselves out using any criteria they wish
  3. If sorting isn't happening in the way you wish, you may want to take some of the openness away and give them a bit more instruction.


The videos, below, are only visible in the WECDSB domain. That is, only teachers in our school board can see the video if they are logged into their MyTools2Go accounts.



  • Open Sort Similarity Cards (pdf) (doc)
Did you use this activity? Do you have a way to make it better? If so tell us in the comment section. Thanks

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