They quickly determined that the angles all had to be equal, but didn't see the relationship between the sides. I found that I had to ask a lot of questions to get them thinking about those side lengths.
me: "Which sides should you compare?"
student: "The two longest."
me: "Can you tell which sides to compare without knowing all the lengths?"
student: "No. Yes... Angles!"
me: "Okay, so now compare them."
The shapes I created were interesting in that several sides on the larger shape appeared to be 1 cm longer than the corresponding sides on the smaller shape. They were sure they had the right answer until I pointed out the side where that didn't work. One group even calculated the differences between corresponding sides:
That was followed up with the second side of the sheet to solidify what they had figured out.
This activity was simple yet pushed some of them to think when they thought they already knew the answer. They needed to be able to explain their reasoning to each other and to me.
Whether they remember any of it on Tuesday remains to be seen!