This lesson set provides a study of story situations that explore the part-part-whole relationship, and through it also, the relationship between subtraction and addition with an unknown addend. Through engaging in this lesson set, students will: make sense of and solve “put together” situations involving an unknown addend using a variety of strategies and representations; determine if the unknown in “put together” situations represents a part or the whole amount in the situation; make sense of and solve “compare” situations with an unknown difference using a variety of strategies and representations; determine the unknown difference as being “how many more” or “how many fewer”; and understand and utilize the relationship between subtraction and addition with an unknown addend. Standards: 2.OA.A.1, 2.NBT.B.7
