This interactive SMARTboard lesson is a great tool for visualizing and subitizing while working on basic math facts. Works great as a small group or large group lesson and then can easily be used over and over in a center or partner work. The lesson/activity becomes more complex as it moves forward. The beginning is more recognition of domino numbers and working a simple addition problem. It then moves on to a missing addend and then students must fill in both missing addends to equal the sum given. All slides are self checking. There is a total of 20 domino addition problems. Addition problems range from sums of 8 to 20. MUST have SMART Notebook to download and use this file.