In this lesson, students use a variety of given inputs to find missing information about a circle. They start by looking for a central angle given an area and radius, then move toward, for example, calculating arc lengths given a sector area and a central angle. Students build intuition about the relationships between angle, radius, and arc length.

Students have an opportunity to make sense of a problem and persevere to solve it (MP1) as they ask questions to extract the information needed to calculate the length of a circle’s radius.