Before students can begin subtracting 2 and 3 digit numbers, they must have a strong foundation of how subtraction works. Using their background knowledge of addition which means greater than or more, they can begin to learn that subtracting means taking away or fewer. Because not all students learn the same way, I like to share multiple methods with my students when it comes to basic subtraction strategies.
Share examples on anchor charts you can refer to throughout your unit. These visual representations will help your learners grow and practice each method to find what makes the most sense to them. Each strategy is introduced one at a time over several days.
Each time a subtraction strategy is added to our anchor chart, I have my students add it to their own personal anchor chart that they complete in their math journal. This allows them to take ownership in the process and always have it as a reference.
Draw A Picture
For this strategy, students will not be using manipulatives but rather will only have access to their pencils. It is important for students to know how to draw a picture to solve for their problems.
They will not always have access to manipulatives but they will always have a pencil. When drawing out problems, I teach them to use dots and mark them out with x’s.
In order to practice this strategy, I give each student a Draw & Subtract page. They will read through the word problems and will practice drawing out the problem and writing the equation.
Counting backwards is when you start at the minuend (larger number) and count back. Students can use a variety of manipulatives to practice this.
As seen on the picture below, I start off using dominos (real ones or the printable ones available here), a number line, and a copy of the Counting Backwards page to practice.
Also, Subtraction Bump is always a class favorite when learning to count backwards! Click here to see more about this fan favorite game for students.
Friends of Ten
When introducing this strategy, I tell students to think about making a ten. We discuss the words “If/Then” and how they relate to mathematical problems.
For example… IF 6 +4 = 10, THEN 10 – 4 = 6 or 10 – 6 =4.
One of my favorite games to play while teaching this strategy is Knocking Down Pins. You can use a bowling set if you have one, but if not 10 cups and a ball work perfectly fine too! Here’s how you play:
- Students will sit in 2 lines facing each other with the bowling pins in between the two lines
- Call on a student to come roll the ball to knock down pins
- They will then create a subtraction problem based on the number of pins knocked down. Ex: If the student knocks down 4 pins, they’ll write 10 – 4 and count the number of pins standing to find the difference
Students can also use play dough to play Subtraction Smash.
- Each student needs a ten frame or double ten frame mat, a can of play-dough, and something to write with.
- Have students build out their subtraction problem on their ten frame mat.
- They will smash the number taken away to solve for the difference.
Using a visual representation of a mat is very helpful when teaching this strategy. Students must be able to recall which section of the mathematical problem is the “part” and which is the “whole”.
We learn this by constantly practicing whole minus part equals part.
If you recall our doubles addition strategy, the same goes for subtraction.
Have student think about their double facts when solving (i.e. 5 + 5 = 10). Students will practice turning their doubles into a subtraction problem to solve for (i.e. 10 – 5 = 5) .
A fun idea to practice this strategy is to play What’s the Symbol!.
- Give each student an index card and have them write a plus sign on one side and a subtraction sign on the other.
- Show them a doubles fact card (addition or subtraction) but over up the action symbol (plus or minus sign).
- Have your students hole up their index card to show what symbol should go in the missing spot.
We just covered a lot of subtraction strategies! Keep in mind that every student learns differently. If a student does better with one particular strategy over the other, let them stick with what works for them. Provide each of your students with lots of opportunities to practice in an engaging way.