So I Tried Clothesline Number lines

I was introduced to clothesline number lines through the #MTBoS.  I inquired more about it and was provided these resources (1, 2, and 3) by @mr_stadel.  After doing some research and making sense of the instructional idea for myself, I decided to try it.

We’re focusing on scientific notation, not just converting and operations but ordering and comparing.  On my first try with clothesline number lines I provided each student with a card.  I asked half of the class to record any number in standard form and the other half of the class write any number in scientific notation.  The goal was to order the numbers from least to greatest.

Students took about 90 seconds to place their numbers on the number line, sliding cards and shifting cards where they felt necessary.  As a whole group, we took a step back to analyze the cards and one student said aloud, “Which end is the least and which is greatest?”  I though to myself, great thinking and we briefly discussed how an empty number line can start and end with any number.  From that part on, while in the heat of the moment, I thought the lesson was an epic fail.  Students remained focus only on the order of the number in scientific notation and did not consider how they compared to the numbers in standard form.  As I tried to draw their attention to this oversight, I noticed some students began to check out of our discussion.  So I summarized our discoveries and moved on to the next activity.

Later as I reflected upon this activity, I noticed the beauty in the oversight.  Although students were able to convert between the two ways to represent large and small quantities, they had not yet been able to apply this understanding.  I also realized students did not have a full understanding of the magnitude of the number when written in scientific notation.  Perfect, I knew exactly what I needed to target!

On the high of the benefits of using clothesline number lines, I quickly developed a plan to present this within a professional learning session I was slated to conducted for other math teachers within my district.  This time, the focus concept would be expressions and equations.

Teachers said their biggest take-aways were:

  • ability to assess students’ number sense when using variables
  • ability to discuss equivalent expressions using the number line
  • connecting kinesthetic number lines to the clothes line number line
  • making the connection to solving equations using the clothesline number line

Many teachers committed to trying this idea within their classrooms within the upcoming week.

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