Your students will use their critical thinking skills to find the unknown on this SMARTboard lesson. Fun and challenging way to get their math minds thinking in a different way. Great to use as a warm up for 10 days (one problem a day); small group; large group; or even an independent center or station. All slides are self checking and the answer slide shows a step by step solution. Addition, subtraction, and multiplication are explored although most problems are a combination of addition and subtraction. Great way to practice fact building along with problem solving. Created with SMART notebook 11. You will need SMART Notebook to open this lesson.