Send your students on a wild goose chase around your room! Each page has a question and an answer. The question leads to another card's answer, which becomes the next question, and so on. These are a little more challenging than some other activities I've seen. There are 14 problems and a sheet for the students to record their work.
I suggest printing off the question pages then folding them over onto itself, so that it hides the question and answer. Students will pick a problem, write it on their sheet, solve it, then search the room for the card that has the solution. If they can't find their solution, they either didn't search hard enough :) or did it incorrectly. It doesn't matter which problem the students start with because they all link around to each other.
The answer on page one is the solution to page 2's question, so I recommend shuffling the pages before you hang them around your room.
This took my students between 30 minutes and an hour (after a 10 minute quiz) to complete all 14 problems. The student(s) who finished first got a prize! My students really seemed to enjoy it, and I'm sure yours will too!