Connecting Proportionality and Covariation, Clip 1, 5:22

• The teacher uses the summary of the photo enlargement problem to discuss covariation with the students. This is a nice opportunity to revisit the concept now that the students have had some practice dealing with proportional situations.
• The teacher is constantly encouraging them to verbalize which ratio is staying the same. Notice that if they use 6 and 8 as the measurements, they refer to those at the original base and original height, respectively. This is important because those measurements are specific to that situation, and thus are not varying.