Subitizing - A Quick Way to Develop Number Sense

Subitizing is being able to instantly recognize how many are in a set (Clements, 1999). For most people we can only subitize small sets (less than five), unless they are in some kind of familiar pattern (perceptual subitizing). For larger sets of numbers we tend to decompose the set into smaller sets that we instantly recognize (conceptual subitizing). Look at the dots below and determine how many total dots there are:

Did you do it without having to count every single dot to make sure of your total? The only way a child can count using most of the manipulatives we use in PreK-2 classrooms, is by counting one-by-one because there is no structure built into the manipulative.

The MathRack™ and Ten Frames have become popular in PreK-2 classrooms because they are built upon groups of fives and tens which allows children to use the structure to help them determine the total amounts shown, or subitize.   Both use the five structure because our ability to subitize ends at five, and we then need to break the set of objects into smaller sets we can subitize. Once children understand that the color of beads on a MathRack™ changes after five beads (or when using a ten frame that when the top row is filled you have 5 items) they use that knowledge to conceptually subitize (they see the parts within the whole).

Children will begin to recognize this as seven because all five red beads are pushed over and two white beads; 5 and 2 more make 7.  The following seven apps are my favorites for helping develop the concept of subitizing, do you have a favorite subitizing app that isn’t on my top list?

Arithmaroo 1: A counting math game for kids $0.99
This app helps build children’s ability to subitize. Level 1 starts off great (numbers 5 and less), but when I got to Level 2 (numbers up to 10) the way that some of their “dot patterns” were arranged did not facilitate seeing groups and instead I was back to counting one-by-one. However, I do like that they use the dot patterns as well as finger patterns (just wish the dot patterns were arranged in more useful ways). Another fun feature is at the top of the screen it shows if you are a Kangaroo(Fast), a Salamander(Medium), or a Turtle(Slow) while you are solving each one. The goal with subitizing is to be a Kangaroo each time (by instantly recognizing) instead of a Turtle (counting).

Dominoes Addition $1.99
This app uses dominoes to help develop children’s number concepts, like subitizing, which then leads into models for addition.

 MathGirl Number Garden $0.99
This app is exactly like Arithmaroo (made by the same company) except the visuals that are used in this app are flowers and the finger patterns are gardening gloves.

Number Rack FREE
This is a virtual Rekenrek, also known as a MathRack, Arithmetic Rack, or Number Rack. Children use the beads to model numbers , subitize, and then to add and subtract. You can add rows so that you can work with numbers up to 100.

Quick Images
Great app that uses dot patterns, finger patterns, ten frames, and rekenreks.  There are different game modes that kids love.

Subitizing Flash Cards $1.99
Multiple activities in this app, but all centered around getting kids to subitize. I don’t like how they fill their ten frame (it is random instead of filling the top row first). The cool feature I LOVE about this app is the teacher tool. You can create your own subitizing cards and save them to your photo library so you can do some quick images activities.

Tens Frame Snap $0.99
Similar to the game SNAP but uses ten frame cards.  There are different games within this app.  My favorites are the matching (snap two cards that are the same) and addition (snap two cards that add to a specific number).