Subitizing

Subitizing is an essential component to building number fluency. Douglas Clements (1999) explains the importance of subitizing in that, "Students can use pattern recognition to discover essential properties of number, such as conservation and compensation. They can develop such capabilities as unitizing, counting on, and composing and decomposing numbers, as well as their understanding of arithmetic and place value - all valuable components of number sense" (pg. 404).
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Example in 2nd Grade

Each day during Calendar Math we add a straw to the ones place and calculate the number of days we've been in school. We update the place value digits as well as the base-ten picture cards that show ones as various arrangements of small squares. When I hold up a new base-ten picture card, seven for example, I ask the students what they see. Some may reply that they see 5 and 2 while others may see 3 and 3 and 1.


About once a week we play subitizing games with rekenreks (math racks). I usually begin by displaying a virtual rekenrek on the SMART Board. I slide the white and red beads to create a number and show the arrangement very quickly! I ask my class what they saw? They often recognize the number right away, but sometimes they might have to combine smaller images together to determine the total number. Next I ask the students to form pairs and use the homemade rekenreks (made using laminated construction paper, pipe cleaners, and beads) to practice subitizing with a buddy.

Challenge!

Introduce subitizing to your students with the below YouTube videos posted by Jeanne Chmelik. Incorporate weekly subitizing fun into your schedule that includes:


- virtual manipulatives and online games

- dot cards, dot plates, dot eggs, or even dot spoons

- rekenreks (math racks)

- dominoes and dice

- ten frames

- subitizing apps

- 'I Have, Who Has?' subitizing card game

Subitizing #1
Subitizing #2

Virtual Subitizing

References

Clements, D. H. (March 1999). "Subitizing: What is it? Why Teach it?" Teaching Children Mathematics. Retrieved from http://gse.buffalo.edu/fas/clements/files/subitizing.pdf