Final answer:
Teachers may use various formative assessment methods such as group activities, math exercises, and conceptual questions to check students' comprehension.
Step-by-step explanation:
The teacher in the provided context may have checked students' comprehension through a variety of formative assessments that allow for confirmation of core conceptual understanding and the application of learned content.
Methods such as Collaborative Group Activities encourage group discussion and practical application of the chapter's material. Figuring For Yourself exercises present mathematical questions that assess and extend the students' grasp of math principles.
Additionally, Thought Questions and Check Your Understanding segments elicit reflections on principles and conceptual questions that require students to apply knowledge to new situations. All these methods contribute effectively to assessing students' comprehension.