This winter, I’ve been working with my first ever student teacher. One of the first things that we did was make a list of different practice structures and the benefits of each one. He had definitely heard of some of them from his MAT program, but several of them were brand new. One of the newbies, was a “Mystery Sum” activity, which happens to be one of my all-time favorites. I got to talking with the other math teachers in my department, and none of them had heard of it either!

Since Mystery Sum Group Challenge Activities are one of my favorite practice structures, I figured I’d share all of the details with you! Be forewarned, I will say it’s the most time-consuming of the practice structures if you’re making it from scratch.

To give you an example of how it works, I’ll walk you through my **Solving 2-Step Equations Mystery Sum Activity** (you can download it for free **here**, if you join my **mailing list**!).

Students work in teams of 4 to complete the mystery sum group challenge. The way this activity works is that there are six suits of cards (I make them with a flower, crown, star, peace sign, lightbulb, and phone but you can really use whatever). Each suit has four cards (one for each student). The cards are actually numbered. I always have it set up where the cards within each suit are differentiated as follows:

Card 1 – Basic

Cards 2 & 3 – Basic/Moderate mix

Card 4 – Moderate/Advanced mix

I do let my students know that each card is leveled so they can pick an appropriately challenging problem to work on. They’re pretty good at self-reflecting and choosing the right card.

Once students are in groups of 4, each student gets a work recording sheet, and each group gets an answer recording sheet. Finally, we’re ready to go. Also, teachers, this part is really important, this is an activity that you absolutely MUST have an answer key pre-made. Students will be checking in with you rapid-fire, so you need to be ready. I always include an answer key with my activities, so you don’t have to do any extra prep!

Now that students are in groups and they have all of their supplies, you’re ready to begin! Each group gets a suit of cards (each suit contains 4 cards). Students will take their designated number, and begin solving their problem on their personal work recording sheet. Once students get their answer, they will write it on the group answer recording sheet. After the whole group has finished their problems, they need to find the sum of all of their answers to the problems within that suit. Once the group has found the sum, they can check in with the teacher.

Now, we’re getting to the part that I LOVE so, SO much about this activity! At this point, the group should check in with you about their sum. If they’re correct, then exchange the suit of cards they’re working on for one they haven’t done yet.

If they’re incorrect, that’s where the magic happens! Don’t tell them anything other than the fact that their group has not found the correct sum. It is up to them to work collaboratively to find the error(s). This activity promotes so many things that are the best parts of math class:

- Collaboration
- Error analysis
- Persistence
- Precision
- Effective team communication

Plus, it’s differentiated! Seriously, what else could you ask for in an activity?

Once a group has made it through all six levels, I like to have them go become helpers around the room.

It’s fantastic to see students progress over the course of the activity. They may struggle a bit initially (which is a big reason why this is a group activity so they have built-in support), but as they progress, suit through suit, they pick up speed and accuracy.

Hopefully, I’ve given you an idea of why Mystery Sum activities are one of my absolute favorite practice structures around.

If you’d like to try out an activity without having to make one yourself, you can download my **Solving 2-Step Equations Mystery Sum** activity, **here **by joining my mailing list! I promise to never spam you, and will only send updates about sales, new resources, giveaways, and the occasional tip or trick that I’ve learned.