Here are some reasons why I’ve written this blog:

- I think math games should be an integral part of math instruction.
- I especially like “low floor, high ceiling” games that are accessible to all students, where learning to play is easy but the potential exists for students to grapple with important mathematical ideas.
- I like games that combine numerical skills with thinking strategically.
- I also like games that have an element of luck to add some extra excitement.

*The Two-Dice Sums Game* meets all of these criteria. It’s one of my long-time favorite games that I describe in detail in my soon-to-be-available new book,

**. But I never stop tinkering with lessons. In this blog, I describe how I taught the game again to a class of second graders, tweaking a few aspects of the lesson, and then used the game as an opportunity for seventh graders to communicate with the younger students. It’s all about continuing to learn as a teacher.**

*Welcome to Math Class***INTRODUCING THE TWO-DICE SUMS GAME IN GRADE 2
**

**Beginning with a Number Talk**

I gathered the second graders on the rug for a number talk about the sums possible when rolling two dice. The students were familiar with using dice to play games. “What’s the smallest sum we can get?” I began. Most knew that it was 2 and it came up when rolling 1 on both dice. “And what’s the greatest sum possible?” I asked. Most knew it was 12. I listed the numbers from 2 to 12 on the board and we talked about whether all of the numbers from 2 to 12 were possible. (This wasn’t obvious to all of the students and it was a good opportunity for them to think about pairs of addends from 1 to 6 that add to each number.) After I recorded all the addition combinations they identified, we counted the numbers from 2 to 12 to see that there were 11 possible sums.

**Distributing Number Strips and Cubes
**Next, I showed the student the strips of paper I had prepared with the numbers 2 to 12 on them, the possible sums from rolling two dice. I had placed the numbers far enough apart so students could place cubes on them. I explained, “I’m going to give each of you a strip and 11 cubes. Put the cubes on the numbers anyway you’d like. You may put one cube on each number, stack them all on one number, or arrange them any way you’d like.” I modeled some options with a number strip and cubes and then distributed the materials.

I didn’t give the students any more information at this time. Sometimes I explain more of the game so students might think about how to arrange the cubes, but with these younger students, I felt that it was best first to make sure they understood how to place cubes. Some students went back to their desks and others remained on the rug. Students arranged their cubes in a variety of ways. It’s typical for students to place one cube on each number. (This happened but I didn’t take a photo of any of those arrangements.)

**Explaining How to Play
**After all students had arranged their cubes, I explained the game rules. I said, “I’ll roll two dice and call out the sum that comes up. If you have a cube on that sum, you may remove it. If you have more than one cube on the number, you may only remove one of the cubes. If you don’t have a cube on that number, then wait until I call out a new sum. The winner is the first person to remove all the cubes.”

I had a few of the students repeat the directions. (I generally do this when giving directions and find it’s helpful to clear up confusion.) Then, before beginning to play, I said, “If you’d like, rearrange your cubes. Once we start playing, you’re allowed to remove a cube if I call the number it’s on, but you’re not allowed to rearrange them.”

**A question:** How would you arrange the cubes to have the best chance of being the winner?

**Playing the Game
**As we played, the students were engaged and excited. There were cheers and groans each time I rolled the dice and called out a sum. I monitored to be sure students were playing correctly.

When I noticed that some students were close to winning, with only two or three cubes left to remove, I interrupted the game. I asked students to report the sums they were waiting for. Everyone seemed surprised that while there were differences, all of the students who reported mentioned the same sums―2, 11, and 12.

I then continued the game until we had a winner.

“Let’s play again,” I said. I added, “You may want to place your cubes on different numbers this time.” Some did and some didn’t. After a few more games, I was satisfied that they all understood how to play.

**Playing Independently
**I added

*The Two-Dice Sums Game*to the math menu as an option for partners and the game was a popular choice. (For information about math menus, read

*Using Math Menus: Some Nuts and Bolts*.)

As students played the next several days, some began to think more strategically about how to place the cubes to have a better chance of winning, using their experience and intuitively engaging with the likelihood of the possible sums. Other students seemed to continue to arrange cubes randomly or would cling to their “favorite number” strategy. All were getting practice with adding numbers from 1 to 6.

**TEACHING SEVENTH GRADERS
**Not long afterward, I worked with a class of seventh graders learning about probability. While I used the game with the younger students to help prepare them for later studying probability, I was interested in providing the seventh graders opportunities to investigate chance, make conjectures, and develop and use probability models. I introduced a variety of activities with dice and also engaged them with a menu of probability explorations.

I didn’t initially include *The Two-Dice Sums Game *on the menu for the seventh graders. I waited until after they had formed some ideas about probability related to two dice and then explained *The Two-Dice Sums Game* I had taught to the second graders. We played the game and talked about how to arrange cubes to have a better chance of winning. The seventh graders were as interested and engaged in the game as the second graders!

I gave the seventh graders a writing assignment: *Write a letter to the second graders and offer them tips for playing the game.* This turned out to be an effective way to assess what the seventh graders understood and also for the second graders to learn from older students.

**FINAL COMMENTS
**This blog includes several changes from the way I described the game in my new book

**(The book will be available in early January 1 but is available now for pre-order.) About the changes: Instead of giving students counters, my colleague Lynne Zolli prefers having students use interlocking cubes that they can stack up on their number lines. (That’s what you see in the photos above.) I tried her suggestion and liked how it worked. Also, this is the first time that I had older students write about their experience, which not only was beneficial for them to reflect on their strategies but also helped the younger students.**

*Welcome to Math Class.*

Marilyn — Excellent. The core of what makes this game so interesting is that you are asking a deep question (understanding probability distribution), then giving all kids a manageable way to incrementally step toward understanding at their own speed. In a social context where they can learn from others. Writing letters to second graders is a great idea; it gives student a real reason to explain their thinking.

You and I have talked, and I’ve certainly always believed that games belong in math class. I want to let you know about Math Monday (http://mathmonday.net), a volunteer-led program I started so every school can have a weekly math game playtime. The format is that there’s a room full of all-age math games, and kids can choose any game they want, with volunteers there to help as needed. It’s starting to take off, and I’ve got the backing of the American Institute of Math, which now oversees Math Circles and the Julia Robinson Math festival as well. I’ll add your number game to the mix of games we give to kids, with a link back to your new book.

Thanks so much for your reply. I love the Math Monday idea — thanks for letting me know.

Very creative. I’ll try it out on my small tutorial center. I hope the kids studying math there will find it fun.