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Steps inquiry

This prompt comes from one of Don Steward's booklets in the Median series. He suggests using the flow chart to begin a structured worksheet investigation. However, in my experience, the prompt can initiate open inquiry that encourages and draws upon the creativity of students.
The prompt is suitable for all classes of secondary school age (11 to 16). It invites students to place a number in the larger circle and calculate the results of taking the steps in the two paths. For less experienced inquirers, the teacher might label the larger circle 'input' and the two others 'output A' and 'output B'. Even if the teacher opts for the more open prompt, communication is easier when the class develops labels for the three circles. 
When asked for comments or questions, students invariably reach the conclusion that, in the case of the prompt, one output is always three more than the other. This realisation acts as a sort of preliminary phase to the main part of the inquiry. The selection of a regulatory card at this point often reveals a great deal about students' mathematical thinking. My classes have tended to select one of two cards. 
  • Either students select find more examples, by which they mean to experiment with different pairs of operations. (The teacher of younger classes is advised to stipulate that only multiplication, addition and subtraction are permissible in the initial phases.) Students go onto induce a relationship between two outcomes.
  • Or students choose prove the prompt is always true, which can lead to the development of algebra directly from one numerical case. If we start with four, for example, the top path gives 4 + 4 + 3 or 2 x 4 + 3 as an output. The bottom path gives 4 + 3 + 4 + 3 or 2 x (4 + 3). The algebraic expressions, then, are 2n + 3 and 2(n + 3), where n is the starting number. As 2(n + 3) expands to 2n + 6, it becomes clear that the difference between the outputs will always be three. 
Students have shown great enthusiasm for finding algebraic expressions. They have then substituted into the expressions to deduce the difference between the outcomes for a particular starting number.
Changing the prompt
Students have changed the prompt in the following ways:
  • Use three steps (to give six distinct paths). Compare the outputs, explaining (and proving) why they are the same or different. [On one notable occasion, a discussion of how many paths there would be for three steps led one student to calculate the number of permutations for all cases up to 20 steps in the search for a rule.] 
  • Use three or four operations and the same operations in reverse - for example, x4 +2 x3 reversed to give x3 +2 x4. 
  • Choose three or four operations and aim for equal outputs
  • Use other operations such as division, squaring, cubing, and so on. 
  • Start with two outputs and aim to devise operations that lead back to the same input.
A classroom display of the steps inquiry carried out by a year 8 mixed attainment class at Longhill High School, Brighton (UK).

Promethean flipchart    download
Smartboard notebook   download
Guided poster Devised by Emma Morgan to guide students when presenting their inquiry (see opposite at top).

Presenting inquiry
Emma Morgan
 writes on her blog that using Inquiry Maths has 
turned her students into "active learners who are fearless and methodical when attacking a problem." Emma has designed  a guided poster for the steps inquiry to help students present their mathematical reasoning. 

Emma teaches in Bangkok, Thailand. You can follow her on twitter @em0rgan.

Classroom inquiry
Year 8 students at The Bishop Wand Church of England School in Sunbury-on-Thames (UK) inquired into the prompt. On the sheet below, three students have changed the operation and explored permutations of three steps.
In a whole-class phase of the inquiry, the idea of summing the two outputs arises (see the top row in the picture below). 1, 2, 3 and 4 are mapped to 13, 17, 21 and 25 respectively and, in general, n maps to 4n + 9. The teacher has started to introduce algebraic terms and expressions as a precursor to proof.

The pictures of the inquiry were posted on twitter @BishopWandMaths.
The inquiry in action
These are the comments of a year 7 class about the prompt. The initial phase of the inquiry started slowly until one student declared "a number at the start would lead to two answers." The teacher introduced the terms input and outputs and then invited the student to choose a number. He chose five, from which the teacher recorded the result of each step (for example, 5 + 5 followed by 5 + 5 + 3) - thereby anticipating the development of algebraic reasoning in the form
n + n + 3. Once the idea of starting with a particular number had arisen, students calculated the outputs for other inputs, going on to note the difference between the outputs and speculate about the differences for other operations. The class used the sheet below to create their own examples, finding that the outputs from each pair of steps are related in the same way. At the end of the first lesson, the teacher asked the class for ways of changing the prompt. This request yielded only one suggestion: change the number of operations. The teacher praised the student for her creativity and the lesson ended.
One student's four-step pathways with algebraic expressions
 and the difference between the outcomes.
In the second lesson, the teacher introduced algebraic notation for the original prompt in order to explain the difference of three between the outputs. This led many students to try the same for their examples. Others preferred to use three or four operations after being reminded of the suggestion at the end of the first lesson. The inquiry ended with students presenting their pathways of inquiry, including the four-step diagram in the picture above.
The responses of Amanda Klahn's grade 4 IB PYP class at the Western Academy of Beijing, China, show a creative approach to mathematics. The conjecture (in purple) that the amount added equals the difference between the outputs is a novel idea. It is true when the other operation is 'multiply by two': 
2(n + a) - (2n + a) = a 
where n is the starting number and a is the amount added
We could extend this to the general case when one operation is 'multiply by b':
b(n + a) - (bn + a) = a(b - 1)

You can follow Amanda on twitter @KlahnAmanda.