Category Archives: MTBoS

Testing the “Open Middle” Waters

I have been itching to try an Open Middle math problem.

As a tutor, I am always looking for ways to enrich and deepen the understanding of the students I work with, as opposed to just band-aiding their current math struggles.  I finally got my chance last week.  I chose this 3rd grade question: Draw three rectangles with a perimeter of 20 units.

First, I asked my student to draw one rectangle with a perimeter of 20 units.  Here is his initial attempt.

G_OpenMiddle_Perim 1








Rectangle…check.  Perimeter-is-the-edge…check.  Perimeter = 20…not so much.

We add the side lengths and he sees the total perimeter is much more than 20.

Aha! #1  “Oh, I get it!”  Immediately, he draws a square and proudly labels each side 5 units long.  Yay!  

G_OpenMiddle_Perim 2






Wonderful!  Now:   Draw another rectangle with a perimeter of 20.

Complete puzzlement.

So, we talk about what perimeter means and I ask Is there any other way to have the sides add up to 20?  Aha! #2, and he draws the following “rectangle:”

G_OpenMiddle_Perim 2b






Hmm.  Okay.  Perimeter = 20…check.  Rectangle…not so much.  So I draw his “rectangle” to scale.

G_OpenMiddle_Perim 2c1





Hmmm.  What’s going on here?  We talk about the properties of rectangles and his next attempt is a rectangle, but again the perimeter is not 20.

G_OpenMiddle_Perim 3a






So, I ask him to try again.  He thinks for a bit and then draws:

G_OpenMiddle_Perim 3





Great!  We have two rectangles with a perimeter of 20.  Now draw another one.

Much less thinking time this time:

G_OpenMiddle_Perim 3b





And we get to Aha! #3, at which point he stops drawing, and starts talking:  “Or, the sides can be 2-8-2-8, or 1-9-1-9, or …!)”  Pretty soon he’s listed all of the different configurations/rotations of rectangles (with integer-length sides) and HE GETS IT!

This was more than an “aha!” moment; it was a groundswell of understanding – like a wave of comprehension crashing on the beach:  I get it!  I get it!  I get it!

And it didn’t happen after creating one rectangle, or even after two.  It required him to come up with three different rectangles before he understood.

SO fun to watch.  It literally made my day.  Can’t wait to try more Open Middle problems!


When is a Line Not a Line?

3rd Grade Line Plot

3rd Grade Line Plot (From K12Math Passion Third Grade Written Assessment)

After a long hiatus, I am finally getting back to my assessment project.  The end of the third grade assessment is in sight!  As I work to understand each standard and turn it into an assessment question, I do a fair amount of checking to make sure (1) I’m using appropriate levels of problems and (2) my assumptions are good.  (I don’t always succeed, but that’s another story!)  This check is particularly important with elementary topics because my credential and most of my experience is with secondary math.

Two of my favorite sites for checking my assumptions are IXL Math and Illustrative Mathematics.  They are both very organized and easy to use.  IXL Math has lots of practice problems for each standard and Illustrative Mathematics has amazing tasks and a great interactive graphic showing the domains across grade levels.  (I’ll be using both of these sites over the summer with my 3rd and 4th grade tutoring students.)  There are others, of course, and I also use Google to research topics.  (If  you have a favorite site, please share it in the comments!)

Thank goodness I checked my assumptions about line plots (3.MD.B.4).  I don’t know about you, but when I think of line plots my brain constructs an image of coordinate pairs connected by line segments.  You know, something that has lines in it.  So, I was a bit surprised when I Googled “line plots for 3rd grade” and images of stacked X’s came up on my screen.  (See example above.)

Okaaaay.  Hmm.  Well, the making-a-line-plot standard doesn’t have an image of a line plot.  So, I did a little digging and discovered that, apparently, in the 3rd grade world a line plot looks like stacked X’s.

Don’t get me wrong.  I think the stacked-X’s-as-line-plot is an outstanding stepping stone between bar graphs or pictographs and traditional line plots.  I understand it’s an important bridge, which will greatly help students make the transition.  In fact, I hope teachers facilitate this transition by eventually asking students to draw a dot at the top of each stack of X’s and connect those dots with line segments.

It’s just the name that gets me: line plot.

I realize I’m a very literal person, and third grade was a LONG time ago, but I think even third grade me would be confused.  “Where are the lines?”

When is a line not a line?  When it’s a third grade line plot, of course.  Anyone can see that.

So Much More Than People Think

To educate

Microsoft Office Clip Art, November 2013

The announcement for Mission #7 of Exploring the MathTwitterBlogosphere happened to cross my consciousness this morning.  The mission: to explore a day in the life of a teacher/educator.   (Thank you for including non-teachers!)   It’s Sunday, my big tutoring day, so I resolved to take whatever happens today and write about it.  I wondered if I would have anything to write about.  This turns out not to have been a problem.

This morning, with latte in hand, I continue unpacking my calculus knowledge so I can preteach the next section to one of my tutoring students later today.   I love this concept – can you love a concept? – that as we process knowledge it becomes compressed, and then as teachers we have to go back and unpack our knowledge so we can help students learn.  This model perfectly matches what I feel in my own head as I learn and process new concepts.  BTW my calculus knowledge has been packed for a very long time!

In the middle of all this calculus, I find out my dad was in the hospital last week and didn’t tell me.  (Sigh.)  He blacked out twice recently, and was planning to drive somewhere today.  OMG.  I make him promise not to drive and wish I lived closer to him, or vice versa.

Tutoring session #1 starts out shaky.  It turns out my student is having a personal crisis.  I don’t ask outright, but wait until confided in.  I then spend 10 or 15 minutes responding with my best growth mindset messages:  this happened only one time; you will do better next time; this event does not define you.  Whew!  I’m able to help the student process the event and move on.  This job is so much more than people think it is.  At the end of the session, I strongly urge my student to “step away from the math” for a few hours, and then go back and review each of the problems before submitting the assignment.  Recognizing the benefit of letting time pass so you can tackle a problem with fresh “eyes” is a good life lesson and only one of many I find myself sharing with my students.

Tutoring session #2 starts out great:  I discover my student scored one of the highest grades in the class on the latest test.  You can just see the increase in confidence and a willingness to try more difficult problems instead of sitting back and saying “I don’t get it.”  Gotta keep this positive feeling going!

As I reflect on the day’s educational interactions, I realize (once again) how much the affective side impacts our ability to be effective educators.  This job is so much more than people think it is.  And isn’t that great!

Scary Real Life Math Stories


Or, Why Rates And Proportions Are Important.

It’s Monday morning.  I am having a medical procedure done in which medicine is pumped into my arm through an IV.  My nurse is calm, efficient, and experienced.  She is also training someone new.  No problem: Everyone is new at one time or another.

After the experienced nurse inserts the IV, the two nurses leave me to retrieve the medicine.  This is the gist of the the conversation I hear through the curtain:

The amount of medicine is 100 ml and it needs to be infused over half an hour.  The machine needs the infusion rate to be entered in ml per hour.  What rate should you enter on the machine?


The medicine is 100 ml and it needs to be delivered in half an hour.  What do you enter on the machine?


Think.  We have to infuse the entire 100 ml in only half an hour.  How many ml/hr do we need to enter on the machine?

Oh, 200!



You can be sure I was paying close attention to this conversation.  And even though the trainee eventually got to the right answer, I was still relieved to see the experienced nurse check the machine.

One thing I noticed:  The strategy employed by the experienced nurse was essentially to repeat the question, with very little modification, and to calmly ask the trainee to “think.”

My approach would have been different.  When the trainee first answered “100,” I would have said something like, let’s think about that.  If we enter 100 ml/hr into the machine, and we have 100 ml of medicine, how long will it take the medicine to be completely infused?  I presume the trainee would have said it would take an hour.  (At least I hope so.)  At that point, I would have said, now if we want to infuse the medicine in half that time, do we need a faster rate or a slower rate?  What rate do we need to enter?  

I think this approach would have made a better connection for the trainee and allow her to see how her answer needed to change.  It would also better model the thinking needed to solve the problem.

What would be an even better way to have handled this situation?

MTBoS Mission #1 – Exploring Functions

Welcome!  Here is my contribution to Math Twitter Blog-o-Sphere Mission #1:  What is one of your favorite open-ended/rich problems?  How do you use it in your classroom?

I was looking for a way to open a discussion of functions with one of my tutoring students last summer and found a lesson on the Internet called The Shapes of Algebra, which (at least in one version) included a great Ice Breaker activity.  (See references below.)  This activity asks students to consider five functions – represented in five different ways (verbal, tabular, graphical, function notation, and as an application problem) – and determine which representations belong together.  One example is shown below.

AfAY1 icebreaker

What I Did

After printing the file, cutting apart the different representations and mixing them up, I gave my student the pile of cards with only the briefest of explanations:  Which ones go together?  It was wonderful to watch how engaged he was as he first figured out what he was looking at, and then went to work puzzling out which cards described common situations.  His initial groupings contained several errors, but he corrected most of them on his own as he worked through the set of cards.  To finish the activity, he taped each set of representations to a piece of paper labeled with the name of the function, creating a personal reference for the rest of our lessons.

In addition to creating a introductory experience with different types of functions, this activity generated lots of great conversations about interpreting graphs, identifying slopes and rates of change, as well as the meaning of function notation.  Each of the five functions are completely different (linear, quadratic, reciprocal, absolute value, and exponential) and nicely set the stage for the rest of my planned function lessons.

How I Would Use It

In a classroom, I would definitely use this lesson as a group activity.  I would create “kits” of the cards so that (ideally) each group would have a complete set for a different function along with lots of cards for other functions so they had opportunities to compare and contrast different representations.  I think this activity would spark a great discussion and I would follow it with The Shapes of Algebra explorations using the Function Explorations document I created.  The document both structures the activity and provides a nice way to collect students’ observations about the way the functions change.  Desmos is a great tool for students to use for graphing the functions, but a graphing calculator (or even pencil-and-paper!) will also work.

What would you do differently?


There are several links for The Shapes of Algebra handout (including one for an online version), but I can’t seem to find the link where I found the ice breaker activity.  You can use my link, or Google (including the quotation marks) “Mary owes her mother $7” and you should find the file.