This is a team game with 3-6 players per team.
The leader writes down a secret number to be revealed at the end of the game. To start the game, the leader gives 2 clues about the number, e.g. “The number has five digits and is between 10000 and 20000.”
The teams are then given a time limit to come up with a guess as to the number. If no team guesses the number, the leader announces whether each team’s guess is higher or lower than the secret number.
Following this, another clue is given, e.g. “The digit in the ‘hundreds’ place is 7” or “the second digit is odd.” The teams are then given 30 seconds to come up with their second guesses. This process continues until the number is guessed.
A great game for reinforcing numeration and number concepts.
The size of the numbers involved can obviously be differentiated to suit the ability of your class.