Teaching Subtraction with Cuisenaire Rod Activity

Teaching Subtraction can often be a mysterious task that you aren’t quite sure how to tackle and even with Cuisenaire rods, it is still a not so obvious task. You think it’s an easy task when you first give it a go, but you soon learn that you set your expectations too high.

This activity I am going to show is an effortless way to introduce subtraction. It is uncomplicated and because it is subtle, your children will take to it easy.  It is great for preschoolers and kindergartners, and I will talk about how to expand this for first graders, too. I came across this activity on an online Gattegno conference, but I added a lot more ways to expand and extend the activity.   

Presentation is Everything

This is by far my favorite subtraction activity for Cuisenaire Rods, but presentation is everything. While children can do this subtraction activity without knowledge of numbers or even being aware of subtraction, if you don’t tap into their world of imagination, this activity may fall flat.

In a very subtle way, this activity will help children gain an understanding of structures, and this will help them with problem solving later down the road. They are building locks and finding the missing keys to unlock or lock their locks.  This is presenting children with algebra, but this let's the child grasp that subtraction is like finding what is missing in an addition problem.  This will help them memorize their math facts faster when they are aware of this math structure.

Of course, children don't like doing things randomly because you say so.  When you present this activity, first pick out a beautiful fairy tale story of a princess being locked up like Rapunzel. Then have them draw a picture of the princess being locked up.  

Now pull out the Cuisenaire rods and show them how to build a lock to lock up the princess in her tower.  Then have the child look for the key to release her from her prison.  Now, princesses might not be everyone's thing.  Be sure to connect to your child's imagination whether its dragons or spy tales.   When you tap into that fantastic imagination, you will have children building and crafting locks for endless fun.  

The simplest lock is just three rods with two rods being the same length and the middle rod being smaller than the other two rods, but let's look at all the opportunities to extend this activity to add more depth.

Subtraction Activity Extended

You can easily extend this activity several ways. You can add more complexity to the Lock and Key activity by adding more than one lock. The student can do 2 locks, 3 locks or go crazy with ten locks.

Another opportunity for complexity is to use more than one block in the middle layer of the lock. This strengthens the students understanding of structures as they begin to see the many ways to build and take apart a number.

Students can gain even more depth by combining more than one lock and adding complex lock layers. To make it more interesting, have students create locks and challenge you or their peers to find the key.

Extending for Older Children​

Notice, there is absolutely no writing happening at all in this activity.  I told you it is a subtle activity. Because Gattegno is more interested in getting the students to see the structures in math, students learn to describe what they see by the color of the rods.  

Before introducing writing, begin with describing their lock for them a few times.  Then have them describe their lock.  You can also describe a lock for them to build.  

An example of describing a key can be: red is the key to unlock the lock because light green plus a purple plus a red makes the same length as purple.  ​Or you can describe the lock.   The lock is the length of blue with the middle layer composed of a green and a purple.  What's the key?

As they begin describing their locks and corresponding keys, you can begin writing down their equations for them using letters.  b (blue) = g (light green) + p (purple) + r (red) or r = b - g - p   In the first equation, you are really describing the lock and then the key.  In the second, you are observing why the key fits the lock.   Either way you or the child describes it, the child should become aware over time that subtraction and addition are apart of the building and taking apart of numbers.  

Unlock Their Imagination for Endless Discoveries

Don’t forget to tap into your child’s imagination by painting stories for them or have them tell you a story about who or what they are locking up. You can also use PDL’s Lock and Key Subtraction Activity which inspires their imagination to create endless locks and keys. Create a wonderfully fun notebook with these activities so they can return to them again and again.

I hope you have a lot of fun with these activities. Want more daily activities like this? Be sure to follow me on Instagram. I love sharing activities that you can add to your daily math routine to make learning more playful and filled with discoveries. Also, be sure to tag me on all your Cuisenaire rod fun!