#SwDMathChat From Patterns to Algebra (part 5)

Inspired by San Diego City Schools Middle Level Mathematics Routine Bank, I started out my school year with Do Nows every day to help build my students' number sense.  I did the number of the day, area models for multiplication of 2 and 3 digit numbers, and mental math strategies.  Then somewhere about mid-November I switched the Do Nows to the Guess My Rule or pattern activities from Ruth Beatty and Cathy Bruce's book From Patterns to Algebra, but feeling sort of guilty thinking I was abandoning my number sense routines.  But the more I thought about it, I realized that these activities are all promoting number sense as well.  My students are always doing some heavy-duty thinking, trying to discover pattern rules and predicting what will happen next, and I see them using some of the strategies they learned earlier in the year.  For my special ed students, these activities are really pushing them to their limits and I'm pleasantly surprised at how well they are doing with all of them.  The very visual and hands-on lessons are perfect for them to make the strong connections they need to move onto the important 8th grade concept of graphing linear equations.  Even though this book wasn't written with the special ed population in mind, it is just what they need to be successful!  (If you haven't read about my earlier adventures with From Patterns to Algebra, please take a look at my 4 previous blog posts!)

This week we continued to work on lessons inspired by this great book.  We started out comparing patterns and finished with beginning our adventures in graphing patterns and rules.  Today I was observed by my supervisor and I think he was pretty impressed with the lesson.  He loved the hands-on aspect and was impressed with my students' ability to answer my challenging questions and make the necessary connections between the rules and the graphs.

We started out the week comparing these 2 patterns to predict which would grow faster and why, even though the first position looked similar.  I had them first identify the rule for each pattern, where they discovered that both patterns had a 5 and a 2.  Then they predicted that pattern B would grow faster because they could see that by position 3 there were definitely more color tiles.  We completed the tables to the right together and noticed that they started out with the same exact number of total tiles, but by position 3 there were many more total tiles in pattern B.  I asked them to see if they could figure out why B grew faster than A even though they both had a 5 and a 2 -- what makes the difference?  They came to a consensus that the reason for the bigger growth was that the multiplier of 5 made the pattern grow faster than the multiplier of 2.

I gave them a few more rules to compare, some with the same constant, and some where the constant with the smaller multiplier was much larger than the other rule's constant, like the one below.  I again asked them to predict which would grow faster, and of course they picked the "x6 + 2" because the multiplier was larger.  We started completing the tables one position at a time and they were surprised that their choice actually got off to a slower start.  We continued the table and eventually saw their choice overtake the other rule to take the lead - they cheered!!  I wanted to make the point that the constant really doesn't matter here - it's all about the multiplier.

The next thing we tackled lead us into my favorite part - we're finally getting to graph the patterns and rules!  As the book outlines, I started them off with patterns with no constants.  I asked them to identify the rule in the pattern (on the left) and think about how we could represent the pattern on a graph.  They really had no idea what I was talking about, so I showed them the graph (on the right).  I reminded them that graphs usually have labels on both axes, so what do we need to add to the y-axis as a label?  One student volunteered that we needed to number it so we could see how many tiles there were.  The biggest difficulty most of my students had with this was remembering to "stack" the tiles one on top of the other like a tower instead of placing them exactly as they were in the patterns.  We discussed why we needed to do this -- so there was a one-to-one correspondence to the numbers on the y-axis.

I love this Post-It graph paper!

Next I paired them up and gave them their supplies:  large Post-It note graph paper, color tiles, rulers and markers.  I had already drawn the axis and position numbers on their graphs for them, but they had to number the y-axis.  I first demonstrated how they had to place their color tiles on the graph lines, not in the spaces between so they lined up with the position numbers on the x-axis.  What we also discovered was the color tiles are just ever-so-slightly smaller than the boxes on the graph paper, so after stacking several tiles, they were not exactly lined up with a line on the graph paper -- we just had to slide each position's stack up slightly to match the next line above it.  Then they needed to draw a dot at the top center of each stack, remove the tiles, and connect the dots with the ruler.  (It's amazing how many students could not draw a straight line with a ruler and how many decided to draw their lines free-hand - ugh!)  Lastly, they labeled each line with its rule.  I had them do this for three different patterns so we could have a discussion about what what different about the 3 lines.  Trying to get them to come up with a word like "steepness" to describe the difference was like pulling teeth!  Then I asked them what it was in the rules that was affecting the steepness.  Most eventually concluded that the larger the multiplier, the steeper the line -- that was a perfect place to finish up that day's lesson.  I felt like they were really making the connection between the rule and the line on the graph - yay!!

Here's one of their patterns built on the graph paper, and the final product on the graph paper (we did not graph the 0 position or discuss the y-intercept this day):

 

Today, as I mentioned earlier, was the lesson that was observed by my supervisor.  We built on yesterday's work by adding the constants and graphing the 0 position.  We discussed where the constant and multiplier tiles should be placed on the graph and decided that the constant should be at the bottom of the stack/tower so you can more easily see that it is the same at every position.  Then we discussed what part of the rule told us where the trend line would start on the y-axis and they discovered that the constant is what determines that.

After a few examples together on the SmartBoard, I turned them loose with their partners to create their graphs.  Again they had 3 lines to graph, but unlike yesterday where I displayed a pattern on the board which they recreated as stacks on their graph paper, today I just gave them 3 rules (no visuals).  They had to decide what the constant and what the multiplier were and show them with the color tiles.  Then they proceeded to draw and label the trend line for each rule.  Each of the 3 rules had the same constant, so they noticed that all 3 lines started at the same place on the y-axis.  Connections, connections...!!

Here's some of their work from today: