On Monday in Math we learned all about fact families or "related facts". We can use fact families in addition/subtraction and multiplication/division.
We also talked about how fact families have three members, but generate four questions.
Students created their own fact families and then had to solve a little nugget of a problem similar to this: Here are two members of a fact family: 8 and 9. Who could possibly be the third member? That's right! The missing numbers could be either 1 or 17.