The purpose of this Warm-up is to prepare students for the Information Gap activity that follows. First, students are given a problem with incomplete information. They are prompted to brainstorm what they need to know to solve a problem that involves sequences. Next, they practice asking for information, explaining the rationale for their request, and persevering if their initial questions are unproductive (MP1). Once students have enough information, they solve the problem.

Tell students that the problem is a part of an Information Gap routine. In the routine, one person has a problem with incomplete information, and another person has data that can help with solving it. Explain that it is the job of the person with the problem to think about what is needed to answer the question, and then request it from the person with information.

Tell students they will try to solve the problem this way as a class to learn the routine. In this round, the students have the problem, and the teacher has the information needed to solve the problem.

• Ask students, “What specific information do you need to find the first five terms and sketch a graph?”
• Select students to ask their questions. Encourage students to use the format of “Can you tell me ?” Respond to each question with, “Why do you need to know ?”
• Once students justify their question, only answer questions if they can be answered using these data:
  • for
• If students ask for information that is not on the data card, respond with, “I don’t have that information.”

When students think they have enough information, give them 2 minutes to solve the problem.

Sample responses:

1	16
2	8
3	4
4	2
5	1

Tell students they will work in small groups and use the routine to solve problems in the next activity.

Math Community
After the Warm-up, display the revised Math Community Chart created from student responses in Exercise 3. Tell students that today they are going to monitor for two things:

• “Doing Math” actions from the chart that they see or hear happening.
• “Doing Math” actions that they see or hear that they think should be added to the chart.

Provide sticky notes for students to record what they see and hear during the lesson.