Lego Perimeter Math

In an effort to help my students understand perimeter for complex figures, my colleagues and I decided to bring in the Legos.  We had been working with rectangles and complex figures by means of technology and visual aides.  So far, the children had a working understanding of perimeter as we used simple squares and rectangles.  But we knew that the complex figures were still troubling many of the children.  If all the measurements for the figures were present, the children could calculate the perimeter.  But if there were missing measurements, the confusion filled the room. 

My colleagues and I talked about the need for using manipulatives, but found that our basic blocks were not sufficient.  To create the figures took up far too much room.  I suppose we could have pulled out the cuisenaire rods, but we wanted the kids to be able to link the blocks, and besides Legos would be so much more fun. 


So, I pulled out the bucket of Legos that I have accumulated from the multiple times that I told my son to pick up his or I would take them too school.  (He didn’t believe me at first, thus I have a full bucket in my classroom closet.  Hee hee.) 

My students’ eyes widened as I began to select a number of 2×4 bricks for the first table.  The volume increased as well.  Eventually, each table had 20 blocks of equal size.  They were given the following problem:

  • Mr. R. has a rectangular room with the perimeter of 20 feet.  One wall is 8 feet long.  Create a rectangle to determine the length of the other three walls.

At first, most of the children began to build up their blocks without really considering what the problem was asking.  They simply were going to put all 20 blocks together.  I reminded them of the task and walked around the room.  As I did, I noticed the work of one of my special education students.  He had properly created the perimeter…without any help from his table.  I was so glad to see it.    I promptly encouraged the class to take a look at his work to get ideas for their creations.  Normally he is the one copying everyone else because he just doesn’t understand the grade level concepts.  From there, the children quickly made the appropriate figure and solved the problem.

From there, we opened up our Activity Workbooks and looked at our next practice page; the page filled with complex figures having missing measurements.  The children worked with matching blocks until we ran out.  From there I piled on the blocks of varying sizes.  I wanted to see how the students would problem solve having different units available.  Some tried to stick to the same size block or used similar bocks, while others looked at the number of “dots” on the Lego.  If the unit was 9 then they would place nine “dots”, regardless of the Lego block.  Some linked the blocks together, while others placed them on their desks to create the figure.  Again, my special education math student worked independently to create the figure as he sees it in his book. (See below.)  This was more complicated, and he wasn’t as successful with the proper measurements, but he was showing perimeter.   His table-mates jumped in to help.


Throughout the class, the children talked, moved blocks, and cooperated to determine the perimeters of the complex figures found on the page.  There were mistakes and successes.  And there was engagement!  Students that regularly sit and let the “smart ones” do all the work or give the answers, were actively participating with their table group. 

Tomorrow they will work with their tables again on a practice test.  This time, I’d like to see them use other strategies, but I will still have the Legos available for those that may still need that extra support.  Eventually, they should be able to transfer this kinesthetic work to mental work. 

I’m glad that my colleagues and I thought of this strategy and tool.  It was great to see my students engage, problem solve, cooperate, and be successful with their math; and it certainly doesn’t hurt that they had fun. 

My son hasn’t used his Legos in a while.  Perhaps I’ll ask him if he’s willing to donate more.  I can’t wait to find more ways to use them in our math lessons.


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