Hidden Numbers Game
Computer Game - the electronic version of the game.
Non-Computer Game - instructions for the non-electronic version.

Hidden Numbers Non-Computer Game


  • To develop the skill of ordering decimal numbers.
  • To raise discussion about decimal misconceptions. (The interviews in the Case Studies show how revealing this game can be.)

Year level: 

Year 5/6 to 8

Group size:

Large or small groups. The game can be played by one person or small team at a time, in front of the class. It can also be played with two teams taking turns. This adds additional considerations of strategy - should the team open a door which will reveal the answer to the other team?


Large cards to hide digits written on the board or a chart.


10 minutes

Activity Instructions: 
The computer game is self-correcting and so can be used for individuals, small groups or in a teacher-led discussion. Without the software, feedback needs to be given by the teacher and other class members and a trustworthy person needs to uncover the digits as requested.

1. The teacher writes a pair of numbers behind the cards, with the decimal points visible and one above the other. Make the whole number parts equal in most cases.

2. Students "pay" (e.g. with points) to reveal the digits they select. A team can only have one digit revealed in each turn.

3. At any stage, the team can guess that the two numbers are equal or nominate which one is the larger.

4. A correct guess wins points. An incorrect guess loses points.

5. Continue until interest wanes. Select pairs of numbers which draw out likely misconceptions (e.g. that only the length of the decimals matter, that 0.32 = 0.3200 etc).