This Instructional Activity is a part of the Lesson 16, Unit 3, Grade 7. Invite the entire class to come up to the front of the room to measure a length of string that is the same length as the distance around the bicycle wheel. Give them the tape or chalk and string, but do not tell them how to use these materials to measure the circumference, at least not yet. The goal is to setup several "ah-ha" moments for students. Give them time to try to wrap the string around the bicycle wheel. They will quickly find that this way of trying to measure the circumference is unproductive (the string will pop off).