Writing Subtraction Word Problems

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SWBAT write and solve a subtraction word problem using drawing, a number line, and an equation.

Big Idea

Sometimes the idea of students WRITING a word problem seems overwhelming. This student-centered lesson makes the process simple, effective, and fun!

Attention Grabber/Introduction

5 minutes

If I'm not 100% sure we are ready for a new activity, I focus on the kids. (And I admit, as closely as I try to watch every kid in every lesson and take time to reflect on the lesson afterwards, I still have lingering questions from time to time).  What better way is there to focus on kids than have them be the stars of the lesson?!

We celebrated our annual Q & U Wedding earlier today, and I use the morning fun to create word problems together. 

5 boys—with their QU hats, just for some festive fun—stand up in front of our group.  I make sure 1 of the boys is the kid who held the Q for the ceremony.

Kids count the 5 boys standing, and I say, “David has to get the Q,” as David walks away from the group with a funny smile.

“There’s a question we ask now…” I suggest.  I call on one of those “safe bet” kids—the ones that we, as teachers, can be pretty certain will “get it” right away, and sure enough, she says, “How many boys are left?”

Kids say, “4!”

“Exactly!  Let’s write that word problem we just made!”

We move to the tables to get started.

Guided Practice

20 minutes

While I work at the document camera, the students have papers to work at their tables.  We are definitely working together!

We write the words for our word problem together, with my model projected on “the big screen.”  I caution students to write small—we have a lot of words to write—but some kids still write their letters… supersized.  Writing isn’t the focus really, so I let them squeeze their writing increasingly smaller as we write each sentence in our word problem.  It’s a natural and logical consequence of writing enormously, and they get practice writing really miniscule letters by the time we finish!

As we write each of our 3 sentences—the statement sentence; an operation sentence, (in this case, subtraction); and a question—the students are supplying the words (MP.2). 

Next, as a group, we write simple drawings to show the 5 boys—we decide on rectangles to show each boy (MP.4).  (I get a lot of student input as we move through the word problem.  It increases ownership of the lesson, which helps engagement and persevering through challenges.)  The kids that finish their rectangles add “QU” for detail.  (This keeps everyone busy while other students are finishing the basics rectangles.)   I circulate around the room, asking kids to count out their hats or commenting on clear, simple drawings.  (I remember back to our first attempt at word problems back with addition, and the students got so caught up in their drawings that they lost track of the math!  Progress is a good thing!)

The kids let me know how to “show” subtraction with pictures, and a student comes up to draw a giant “X” over one of the rectangles on “the big screen.”

Next, as a group, we move on to the number line.  I stress that once again, we are using an important math tool with the number line (MP.5).  I interject—“What about those pictures?”

One friend compliments my drawings, but another kiddo raises a hand, “They are tools, too!”  (“Yes!” I mentally exclaim.  This is reaffirmation that even when it seems like we are talking about MPs a million times, the kids do begin to understand.)  I elaborate, “Yes, the pictures represent the problem!”

The students tell me to begin at 5 on the number line, and a different student tells me to go back 1.  This is where I am particularly appreciative of the fact that I had one specific kid as the “take away” in this critical first subtraction word problem.  As I circulate around the room to check number lines, when students move back 4 places, I can inject, “There are 4 Davids?!?”   Students giggle and immediately self-correct.

A student models on “the big screen” how 5 – 1 = 4 looks.

Finally, we write the equation, which I pair with the term “number sentence” for clarification, (MP.6) on the bottom of the page.  It’s our last step in our word problem, and I am quick to circulate to make sure all students are writing minus signs and putting 1’s and 4’s in the correct places.  I say, “Read your equation—number sentence—to me!” and students recite the equation that goes with our word problem.

Independent Practice

15 minutes

I always make sure these recording sheets are doubled-sided when I copy.  My goal is always to have one Guided practice as a group, and then an opportunity for students to work more independently to show what they know.

Unfortunately for me today, Friday is a short day for math in the best scenario, but it turns out that a number of our lovely wedding guests were involved in some sort of incident on the playground at lunch recess, and math is interrupted with the disruption from recess.  It’s such a bummer when other issues interfere with math!  (Actually, we all love math, and when I let students know that we will have to cut math short, students audibly complain, “Aw!” some say, or “Not math!  It’s my favorite!”

If this would not have happened, I would have given students the choice to team up with one person at their table—although both partners in a team would need to complete a recording sheet to ensure 100% student participation—or students could opt to work independently.  I move around as students make their work decisions to ensure that students wanting/needing to work with a partner do not have hurt feelings if their desired partner chooses to work alone.  Sometimes I work to create pairs so that students are successful, but it’s always fun to see students practice independently.  Again, ownership is important. 

Then, either pairs of students or individuals would work independently to create unique word problems.


5 minutes

If we had time for independent practice, students sharing their work would be our closing.  Since our time was cut short today, our closing is talking about student ideas for what we could have—or would have—made for our word problems. 

We are all still in “Q & U Wedding mode,” which is fine, and students come up with some fun ideas.  One girl mentions the kids in the quartet—the group of 4—and 2 girls were too loud.  Ha!  I love that idea!

Someone mentions the 100 cupcakes that I baked for the reception, and I mentioned that while, we did have a ton of cupcakes, it’s hard for me to keep track of that big of a number.  We choose 10 kids with cupcakes as our number for the word problem.

All of the negotiating and reinforcing remains very student-centered, and I interject my constraints only when the kids get a little off track—or start talking about hundreds!  As always, I never tell kids they are wrong, but after affirming the student’s ideas, I pose a suggestion that students tend to embrace.

Finally, we wrap up the lesson, the day, and our week with one silly question:  I ask, “There was one amazing class of kindergartners who had a really big day but still did some fantastic big kid math.  That class had to go home for the weekend.  How many classes were left?”  The kids laugh and yell, “Zero!”