I was really surprised to see the different strategies students used to find the "1" on the yarn number line. I started with that, assuming that they would simply fold the yarn in half and mark the spot with a 1, just as we did with our paper fraction strips.
However, only one group did that right away. Some tried a "guess and check", by placing a finger where they thought the middle was, and then folding to see if both sides were the same. Another team asked for a yard stick so they could measure and divide. One group just eyeballed it!
I am constantly reminded why simple, yet powerful, tasks like these are necessary. When students are truly asked to apply what they know and use teamwork to accomplish a task, I rediscover that I should never assume that I know what they know based on work on a paper. Seeing them in action and listening to their discussion is the authentic assessment of their knowledge.