Proportional Reasoning is so cool!

This image is from the “Grocery Store, Stamps and Measuring Strips” Context for Learning unit.  I love this unit and think it is a great way to introduce multiplication to students.  At the end of the unit, students are asked to look at this image.  (Note:  I am only including part of the image because this is not my work and I don’t want to violate copyrights!)

We had done all the proportional reasoning work before this:  figuring out how tall or long everything on a city street (trees, a bus, a few buildings) might be in relationship to 4 foot tall Antonio.  It was time for some final assessment.

“How many design elements are on the curtain?” I asked. One image shows a full extended shade, with 16 (maybe 20?  I forget)  oranges in an array.  The grade 3’s easily told me the total, and explained how they had counted.  Lots of multiplying I was very happy to note.  But they said there were 14 stars on this shade,  and 12 or maybe 18 diamonds* on the other curtains. They debated it for a while.  Then I said, “What if I stretched that shade so it covered the whole window, just like this one with the oranges?”

Blank stares.  The 5 of them looked at each other.  They looked at me.  They recounted the 14 stars and 18 diamonds*.  They  weren’t sure what I was asking.  “Well, we can see part of the window in each of these, and there is light coming through.  But what if the curtain was closed?  What if we could see the whole shade?”

They thought some more.  They used their fingers to measure.  They finally decided that if there were 12 on one curtain, there must be 12 on the other, and 2 groups of 12 = 24. . The roller shade wasn’t as easy, but once they figured out the curtain they had a strategy. “I think,” said one, “that there would be 3 more rows of stars.  So thats 7+7 doubled, plus 7 more.” OH MY GOODNESS!  Proportional reasoning AND partial products???  I could not have been happier.  Everyone agreed, then took turns explaining how they’d counted the stars and diamonds.

I’m calling this unit a success!

 

*We are calling them diamonds instead of rhombuses because they don’t have parallel sides that are straight, and the angles aren’t right for rhombuses.

Just about every Tuesday I blog for the Slice of Life challenge over at Two Writing Teachers. You can read more posts on that blog.

We can make our own number lines!

I’m not going to lie:  making the jump to drawing number lines independently has taken a while!  All the grade 2s can explain what I am doing on a number line, and all of them (ok, most of them) can describe a strategy and when I draw it on a number line they confirm I have drawn what they were doing in their heads.  But to make their own?  That’s been hard.

We had completed all of the activities in “Ages and Timelines”, one of the Context for Learning Units, and people were still referring to tools (hundred chart mostly, they they tried to use math racks unsuccessfully) so I wanted to spend an extra week just talking about how to use that number line AND draw it independently.

One day last week, I created some Smart Notebook slides and we all sat down the chalkboards.  Here’s the first one,along with some notation to show that people were flexible with strategies…they used both addition and subtraction to find the answer. I will say that those who added were surprised some had used subtraction, and those who subtracted were surprised that addition could be used, so we had a great conversation about this slide! (Oh, and we are collecting paper towel tubes for science! 🙂 )

Here is another of our questions:

I wandered around and captured some number lines.  Now, this might not be beautiful to you, but darn it!  It is gorgeous to me!  Look at the line, the iterated jumps, the acknowledgment that 4 jumps of 1 is the same as 1 jump of 4…*sigh*  I’m smiling again just thinking about it!

 

I caught one person who was struggling, and handed that child a hundred chart, with a 25 chart on the back.  For this problem, this child was able to use the 25 chart, but for later problems, had to use the 100 chart, and did!

Another beautiful number line… Another great demonstration of the iterated units drawn evenly and there even arrows on the end!

 

One of the most amazing things that happened is shown here.  One child had a 100 chart and was using it well.  Another had no strategy and was looking around the room to see if she was alone in this dilemma.  As soon as she spotted the 100 chart, she scooted over to it.  However, upon arrival, she realized she wasn’t sure what to do.  The other child showed her!!!  (There is a sock on one child’s hand because we use them to erase the chalkboards!)

So, it took us an extra week, and I am quite sure the number of grey hairs on my head has doubled since March Break. Next week, mixed in with some probability to math workshop centres, I am going to be sitting at a table interviewing these lovely grade 2’s to see what they can really do all on their own.  Can’t wait!