Subitizing is the ability to instantly see how many in a small collection of items without counting. Dots on a die, shapes on a playing card, number of fingers held up on a hand, are all examples of subitizing in action. In order to subitize successfully students need to see the whole as a collection of objects as well as the individual units. Subitizing is considered to be a fundamental skill for supporting students understanding of number and ability to perform number operations.
In the primary years students should be given regular and consistent opportunities to subitize in order to build their skills, improve number sense and lay the foundation for future mathematical learning. In kindergarten numbers to 5 should be focused on for instant recognition. Once students are familiar with familiar representations of 1 to 5, larger collections can be used to encourage students part-part-whole thinking. For example, on the card below students may instantly recognize a three and a four and then add the numbers together to know that there is a collection of seven dots on the card.
As the collections get larger students can be encouraged to use their estimation skills to think about “how many” and “how do you know”. Our Saskatchewan Curriculum refers to this fundamental skill through several outcomes from Kindergarten to Grade 2:
- Kindergarten- NK.2 Recognize, at a glance, and name familiar arrangements of 1 to 5 objects, dots, or pictures.
- Grade 1- N1.2 Recognize, at a glance, and name familiar arrangements of 1 to 10 objects, dots, and pictures
- Grade 2- N2.1 Demonstrate understanding of whole numbers to 100 (concretely, pictorially, physically, orally, in writing, and symbolically) by:
- representing (including place value)
- describing skip counting
- differentiating between odd and even numbers
- estimating with referents
- comparing two numbers
- ordering three or more numbers.
This video is an excellent example of a kindergarten teacher who is using Quick Images to build on her students subitization skills, and create opportunities for mathematical conversation.