The process: the class mebers take turns giving me an "input" number. For every input I receive, I will tell you the "output" number. Thprocess will continue until a class member has figured out what rule I am using.

For example:

 

Student says "12", and I say 23.

Another says "8" and I say 15.

Another says "10" and I say 19.

......

Finally, a student recognizes my rule and says "multiply by 2, then subtract 1"

As evidence the student points out that 2(12) - 1 =23, 2(8) - 1= 15, and 2(10) - 1 = 19