Guess My RuleToday I started with the number times two minus three. Inputs came from all over. 12, 5, 10, 1... some shock at a negative answer. I encourage the students to record the results, hoping that it will lead to some ideas about what inputs to suggest. Organizing data is not a natural tendency. At one point they started asking 30, 40, 50...
Any number of players
A rulekeeper makes up a rule that gives a number output for a number input. (It should be a function.) Players take turns giving an input, and the rulekeeper tells them the output. If a player wants to guess the rule, they tell an input and what the output would be. If they're right, they guess the rule. Then that player makes the next rule.
This is a great game for teachers and students alike to do in algebra courses. It gets students use to other students thinking and lets them work in partners and groups to come up with solutions to their own problems. This same skill set would work well with any graphing activity or any other higher level thinking set such as logarithms or quadratics. Check out more here: http://mathhombre.blogspot.com/2012/05/guess-my-rule.html