In this Number Talk, Fran Dickinson engages his 5th and 6th grade students in divining the function from the input and output numbers. As the learners guess input numbers, the educator generates the output number. After each guess he has one of the learners “graph the point."

Commentary by Fran Dickinson

"They had done two previous number talks involving 'guess my rule.' The difference in today’s number talk was the graphing of the coordinate values. In our planning, we decided to set parameters for the learner guesses to keep all of the points in the first quadrant. We had only recently begun investigating coordinate pairs and we thought it would simplify things to have the learners focus. It was interesting to hear all of the different opinions of how to state the rule. I think this illustrates where we were as a group as far as our familiarity with algebraic expression goes. Great conversation between Eric and Sam about 3 groups of x versus x groups of 3. As we wrapped up the number talk the learners mentioned many different ways of representing the rule: x3 – 3, times 3 minus 3, 3x – 3."

See Clips From This Lesson

• Introduction (Part A)
  
• Introduction (Part B)
  
• Introduction (Part C)