This is a ready to use subitizing activity with your students. It shows dots in various colors and formations and you quickly project each slide and have students yell out their answers. You can download the presentation and make changes to better meet the needs of your classroom. For example, the first several slides ask students to yell out the how many blue dots they see. You can change it so some ask for blue and others ask for red, so that the students have to think a little bit harder.
This article, by Marilyn Burns, calls on our new standards to emphasize the ever-increasing importance of number sense in the classroom. It defines what is now being expected of our students and presents applicable strategies for teachers to incorporate number sense into their everyday teaching. It also provides numerous examples of problems that can be used in the classroom at various grade levels
This is a site that has over 200 days of estimation questions that get students thinking about what makes sense. It requires students to come up with a value that is too low and a value that is too high before settling on their official guess. It asks students to justify their answer before submitting. As you and your student progress through the problems throughout the year, you can monitor progress to see if your students are improving.
Classroom Focused Software has a designed a set of number sense apps that are iOS compatible. These apps include number patterns, ten frames, and word problems to name a few. Most of the apps are free but there are are a few that cost $0.99. These apps are a fun way for students to practice basic number sense independently.
Subitizing, a skill that children start to develop from a very young age, means to instantly determine a quantity without counting. This article explains the two different types of subitizing and also gives examples of activities that help to build the skill. Introducing subitizing activities at the secondary level for just a couple minutes a class period, students get additional practice while improving their innate number sense.