Mental math guess my number

It's math time! Here is a game I play with one I tutor and also a variation of it to practice mental math. Guess my number is a great game to have in your teaching arsenal. All you need is a hundreds chart.

 I had one in my favorites on my starboard (cheaper version of a smart board) so I could pull it up quickly when there was a free moment in class and I needed a time filler. So to play you (or whoever is running the game, I'd usually start and then whichever student won let them take over) have to have a number in your head. Then students take turns guessing. They can guess specific numbers (such as 2 or 67) or they can ask any question that can be answered with a yes or no (such as is it an odd number). Before we played the first time, we brain stormed all the different questions we could ask. Here are some examples: even or odd, greater than or less than, place value (is there a 2 in the tens place?), perimeter. As they guess I cross out any numbers guessed to help us keep track. Pretty easy, right? My students always loved it and it was simple and got the kids thinking. We even dove into what question could you ask that would knock out the most numbers? If I remember correctly, asking if it was a two digit number when it wasn't took out the most numbers. 

I have used this game now with the boy I tutor but I changed it a little to help him practice his mental math. Instead of me being in charge, he was. He picked a number (and whispered it to his cousin in case he forgot) and then I started asking questions. However my questions were a little different. I asked him mental math question like, is it 20+4? What about ten less than 67? Could it be 5+4? Usually he complains when we do math but since it was a game it was fun! And after a while he started to get really quick!

That's it! Hope I helped you learn a new way to use one of my favorite tools in our math toolbox, the hundreds chart!