Have a variety of 10-20 piece puzzles available. Have children work in pairs with children who have lower number concept comprehension using the puzzles with fewer pieces. The adult needs to provide some instruction before doing the activity. Children need to understand the concept of flat and a corner. The adult needs to define and illustrate these concepts before beginning.
Place all of the pieces in front of the children. 1) Ask the children how they could divide the pieces into two groups based on the side of the pieces. Let them study the pieces and make suggestions. When someone says straight (or flat) and curvy, say, “Great! Make two sets with one set of straight sides and another set of curvy sides.” 2) Then say, “Now look at the set with straight sides. Is there a way you could make that set into two groups? If no one suggests it, say, “How about pieces with two straight sides? Those are corners!” Have child find all the corners and line them up. Then have them find all the pieces with flat edges and line them up. Finally line up all the curved pieces.
The adult walks among the pairs and listens to the comments and problem solving. She takes notes on individual children related to the skills in this area. The child should be able to create distinct groups or sets relating to characteristics of items.
Parents are not likely to do similar activities, so early childhood educators need to use every opportunity in the day to give children practice with adding to and subtracting from groups or sets. (Total number of coats, number left; single mittens, number needed; total drink cups needed, how many more after 3 set down, etc.)
 North Carolina Department of Public Instruction, 2015
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