In this lesson, students use the Information Gap language routine to decide on and ask for information needed to solve a problem. The Warm-up introduces students to the Information Gap routine and gives them a chance to practice their questioning skills with teacher guidance before working with a partner in the next activity. Students will also practice using their knowledge of angle pairs and triangle properties to solve problems about the relative lengths of sides in a triangle. Students may experience some frustration if their initial questions are unproductive and will practice making sense of and persevering through a problem (MP1). Students will also attend to precision in their language as they communicate with their partner (MP6).