When you click a number, the other numbers in the same row and column will be blocked out. After you click the third number, you will see four numbers left. Find the sum of these four numbers. Try it again. What do you notice? Can you figure out how this works? Can you make another puzzle like this with a different sum?
This is something I used to use with my students if I needed them to remember a date for a field trip or an upcoming assessment. A colleague shared this idea with me a while back.
