In Common Core math, 10 is the most important number that a kindergarten student will learn. It is important because it's the foundation of how you say and write numbers; it's the number at the heart of the place value number system.
In the place value number system, a limited set of symbols (called digits) builds numbers (0, 1, 2, 3, and so on up to 9) and you can write all numbers using these symbols. Most importantly, the values of these symbols change depending on where they appear in the number. In other words, their location (place) determines their worth (value).
Because ten is so important, kindergarteners spend a lot of time noticing it and using it. Kindergarteners may represent ten in a ten frame, as shown in the figure.
A ten frame consists of two rows of five squares. In the squares, children can place counters — usually of two colors. In addition to helping students notice 10, ten frames can also help them identify and remember combinations making 10, such as 6 + 4.
They may represent 10 with their fingers or toes. They certainly can represent 10 by emphasizing 10, 20, 30, and so on when they count past these numbers, and they count by tens to further emphasize the importance of 10.