Oh, no! There is a stranger in the house! Three of these numbers live together and make addition and subtraction facts. Students must figure out which number does not belong to the family. They can record their answers on the worksheet or you can laminate the mat and use dry erase markers. Click to see the "Stranger Number" fly into the robber's sack. Click again to see how the remaining numbers work together in addition and subtraction sentences. This set includes a blackline worksheet for reproducing and a colored mat for laminating. There are individual powerpoints teaching facts of 5, 6, 7, 8, 9, and 10. There is also a review powerpoint with mixed facts. This can be used with whole or small groups.