This Instructional Activity is a part of the Lesson 21, Unit 7, Grade 8. Ask students how they were able to determine the volume of each composite solid in Exercises 1-4. Select a student (or pair) to share their work with the class. Tell them to explain their process using the vocabulary related to the concepts needed to solve the problem. Encourage other students to critique the reasoning of their classmates and to hold them all accountable for the precision of their language.