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Twos to Nines Challenges

Day one and two are in the books! I’ll share a bit more about what I did with my classes on the first two days in a later post, but I want to go ahead and share the mathematical challenge I used with my students on the first day since I have got several questions about it on twitter.

twos to nines number challenges

This summer, my husband and I ran across a treasure trove of puzzle books at Goodwill. We *had* to buy them. As Shaun was driving us home, I flipped through the books and would occasionally pose puzzles for us to solve together in the car. We had a lot of fun with this, and in the process I found some puzzles that would be PERFECT for use in the classroom.

One of my favorite new puzzle books from this Goodwill trip is 100 Numerical Games by Pierre Berloquin. If you don’t believe me that this book is awesome, just take a look at who wrote the foreword. THE Martin Gardner!

You can a free peek at some of the puzzles in the 100 Numerical Games book by using the “Look Inside” feature from Amazon.

Screenshot of Puzzle Inside 100 Numerical Games Book.

One particular set of puzzles which is sprinkled throughout the book really caught my eye.  This version was based on the number two, but the book also featured puzzles for the numbers three through nine.

Twos Challenge Puzzle inside 100 Numerical Games Book.

The task is to use exactly four twos (or threes, fours, etc) to make each target number. Add arithmetical symbols between the numbers to make every equation true. You may use plus, minus, times, and divide symbols, as well as parentheses and brackets for grouping.

Originally, I thought about turning this into a puzzle for my puzzle table, but I never got around to it. Fast forward to this past week. I needed an activity to do on day one, and I decided I wanted to do something a bit different than what I’ve done in the past. For reference on past activities, check out my post on 30+ Ideas for the First Week of School!

Google slide reminding students we do math everyday.

One of the messages I communicate to my students on the first day of school is that we do math everyday. I can’t just say this. I also have to give them math to do on day one.

Google slide asking students if they are ready to do some math.

Yes, there were some groans. We carried on anyway.

My students are arranged in six groups of five, so I decided to set up six challenges around the room. The book featured challenges using the numbers between 2 and 9, so this meant that I had not used the challenges based on the numbers 8 and 9.

To introduce the task, I threw the Eights Challenge up on the TV.  (It’s going to take me a while to get used to saying TV and not SMARTBoard!)

Eights Challenge Puzzle Instructions.

After a quick overview of the rules, I gave them a few target numbers to work towards.

Eights Challenge Puzzle - Four Questions.

Students quickly got to work. Some grabbed paper and a writing utensil. Others got out their graphing calculator or phone calculator. Still others just sat and thought about the task.

Within a couple of minutes, a student in each period would announce that they had found the answer to 10. I asked them to read me their solution so I could write it on the board.

Almost every single time, I ended up hearing 8 + 8 / 8 + 8 = 10. So, I would tell them that we needed to check their work. This was when I asked them what the order of operations says that we need to do first. Unanimously, the class would say divide. Then, a bit of panic would set in. 8/8 is 1. So, 8 + 1 + 8 is 17, not 10.

Without me saying a word, the class would start to suggest either a different way to solve the problem OR a way to salvage this attempt. It usually wasn’t long before someone would suggest that we could use PARENTHESES! So, from this, I learned that we do know our order of operations. We’re just a bit rusty, but I can deal with that.

After the class found a few of the solutions for the Eights Challenges, I decided to change things up a bit. I told them that now that they understood how the puzzle’s structure worked, it was time to try a

Google Slide reading "Your Turn!"

Around the room, I had marked off six four-foot sections of white board space so that each group of students could have their own space for working problems throughout the year.

At each station, I had posted a challenge based on a different number.

Twos Challenge Hanging on Dry Erase Board.

I typed up the instructions for each challenge. My students didn’t really need this since we had done part of the eights challenge as an example, but I did see a few groups reference it. One group used their dry erase marker to actually write symbols between the numbers. Good thing I laminated them!


drawing of laminator machine with text "laminating recommendations"

A laminator is a MUST-HAVE for me as a math teacher! I spent my first six years as a teacher at a school with a broken laminator, so I had to find a way to laminate things myself.

I’ve had several laminators over the years. I currently use a Scotch laminator at home and a Swingline laminator at school.

I highly recommend splurging a bit on the actual laminator and buying the cheapest laminating pouches you can find!

Then, I typed up the target numbers that students had to find. I thought about making them into magnets so the students could move the target numbers around, but I wasn’t sure where all magnets were. Let’s just say that moving classrooms sucks. I can’t find anything right now!

I ended up just taping them to the dry erase board. This worked just fine. Most groups left the numbers stationary and just wrote their solutions next to the appropriate number. A few groups did move the numbers around.

The tape stayed sticky, so they were able to change the number positions without any issues. Since this activity went SO well, I think I will definitely add magnets at some point.

number cards taped to dry erase board for twos to nines challenges.
threes challenge hanging on dry erase board.
Twos and Threes Challenges Hanging on Dry Erase Boards.
Sixes and Sevens Challenges Hanging on Dry Erase Boards.
Wall of Math Classroom Featuring Twos to Nines Math Challenge.

Each table group chose a different number based challenge to work on. They instantly got to work, and the room was soon abuzz with awesome conversations. Students were excited and joyful as they found various solutions.

Students were checking other students’ ideas and pointing out any issues. Lots of parentheses were being used. Were all their answers perfect? Nope. But, it’s day one, and it gave me a great snapshot of where my students are starting from.

Student Answers to Twos Challenge.

It was the first day of school and every kid was engaged. In fact, I would say this was the most engaged my students have ever been on the first day of school. This was my favorite first day of teaching EVER.

Sample Answers to Sevens Challenge.

Check out this awesome group work!

Students Working on Twos to Nines Challenge in Math Classroom.
Students Working on Twos to Nines Challenge in Math Classroom.

Each group was given one dry erase marker and one graphing calculator to encourage collaboration. Every few minutes, I would announce “SWITCH!” This meant that the person holding the marker needed to pass it to another person in the group. The calculator person did the same thing.

Student Work to Twos to Nines Challenge on Dry Erase Board.

Every once in a while, I would introduce a new twist. About five minutes into the activity, I had the groups pause and look at me. I instructed them to nominate one volunteer from each group. This person was to hold their hand up so I could ensure that I had one volunteer from EVERY group. They asked what they were volunteering for. I just said “You’ll find out soon.”

Sample Solutions to Threes Challenge.

Once one hand was up from every group, I informed the class that these students would be rotating one group clock-wise. So, each group would lose one member and gain a different member. There were a few groans with this announcement, but students complied.

I was excited to try this strategy since each group was working on the same type of challenge, but no two groups had the same problems to solve. This meant that the new group member could bring STRATEGIES from their previous group, but they could not just bring ANSWERS.

Sample Solutions to Fours Challenge.

After a few times of rotating a single group member, I changed things up yet again with having the entire group rotate to the next station. I did run into a few issues that I hadn’t figured out how to handle beforehand.

The groups assigned to the challenges based on lower numbers (2s, 3s, and 4s especially) were sometimes able to completely finish their challenge. When this happened, I did one of two things. In my smaller classes, there was often a challenge that had not yet been started. In these classes, I sent the finished group to this untackled challenge. In my larger classes, I had the finished group split apart and join other groups.

Sample Solutions to Fives Challenge.

The Sevens Challenge ended up being the most difficult for my students to tackle. Often, there would only be two or three target numbers solved by the end of the class period.

Student Solutions to Sixes Challenge and Sevens Challenge.

Free Download of Twos to Nines Challenge

Want to try this activity with your own students? You can find where I typed up the challenges in two different formats: Google Slides and PDF (below). I hope your students enjoy it as much as mine! This activity had my students finding joy in solving tricky math problems. My job is done.

Twos to Nines Challenges (PDF) (12093 downloads )

Digital Adaptations of the Twos to Nines Challenge

Google Slides

The Twos to Nines Challenge has been turned into a Google Slides activity by Meghan Smeenk. Check it out here.

Google Slides Version of Twos to Nines Challenges.

KellyLove shares a slightly different Google Slides version.  

Google Slides Version of Twos Challenge.

Desmos Activity Builder

Scott McEwen has created Desmos versions of this activity as well. Each challenge is a separate Activity Builder.

Desmos Activity Builder Version of Twos to Nines Challenges.

Puzzle Solutions

I intentionally do not make answers to the printable math puzzles I share on my blog available online because I strive to provide learning experiences for my students that are non-google-able. I would like other teachers to be able to use these puzzles in their classrooms as well without the solutions being easily found on the Internet.

However, I do recognize that us teachers are busy people and sometimes need to quickly reference an answer key to see if a student has solved a puzzle correctly or to see if they have interpreted the instructions properly.

If you are a teacher who is using these puzzles in your classroom, please send me an email at with information about what you teach and where you teach. I will be happy to forward an answer key to you.


Monday 19th of August 2019

What class did you use this for?


Wednesday 31st of July 2019

Is there an answer key available for the two to nine challenge? It is an awesome activity, however, I am even stumped on a few of them... yikes :)

The McClelland Gang

Sunday 26th of August 2018

Thanks so much. I might use this as an activity to do when I have a sub after an assessment day.


Wednesday 22nd of August 2018

hi there! just to clarify. did a group work on only one set of numbers? Thank you!

Pritam Paul

Tuesday 21st of August 2018

Best Math Puzzle

Comments are closed.