The purpose of this Number Talk is to elicit the strategies and understandings students have for adding within 1,000. These understandings help students develop fluency and will be helpful when students create their own Number Talk routines.

In the Activity Synthesis, discuss what students know about the Number Talk routine and what they need to think about to create a routine like the example.

• “¿Qué saben sobre la rutina ‘Conversación numérica’?” // “What do you know about the Number Talk routine?” (It always has 4 expressions, and we find their values in our head. Sometimes we can use the same method for each expression. Sometimes we can use the first couple of expressions to help us find the values of other expressions.)
• Consider asking: “¿En qué tendrían que pensar si fueran a diseñar una rutina tipo ‘Conversación numérica’ como esta?” // “What would you have to think about if you were going to design a Number Talk like this one?” (How one expression might relate to the next. What strategies might make it possible for someone to find the values mentally. Whether it's possible to use one expression to find the values of other expressions.)
• Record and display responses for all to see.

The purpose of this activity is for students to reason about subtraction and write another subtraction expression to complete a partially-completed Number Talk routine. If there is time, students can facilitate their Number Talk with another group. Students are given three expressions and prompted to think of ways that they could be evaluated mentally. They then write a fourth expression, the value of which they could use similar reasoning, or the values of the first three expressions, to find.

The purpose of this activity is for students to reason about addition and apply their reasoning to complete a partially-completed Number Talk routine. This time, students are given addition expressions and are asked to think about how the values of the sums could be found mentally. They then write two new addition expressions to complete the set.

The purpose of this activity is for students to write a sequence of three subtraction expressions to complete a Number Talk with only one given expression. As in earlier activities, students consider strategies that they or others might use to mentally subtract numbers within 1,000. 

The purpose of this activity is for students to design a Number Talk from a blank slate. They can choose to write addition or subtraction expressions, but still consider possible ways that others might find the values of the expressions mentally. If there is time, allow students to facilitate their Number Talk with another group.