Love this idea! What's the number? Kids ask questions like Is the number greater than/less than....? Is the number between ___ and ___? Is the number in the tens place ____? etc. No two questions in a row can make the same comparison. Or students may ask in number sentences- - Is the number 5+1?
I made mats like this and my class loves to play. We keep score on the board for who wins each 'hand'. I call out, "Draw 2 (or 3) cards and make the least/greatest number possible." I also made one which includes thousands, for later.