Guessing Jar Supplies
As you can see in the picture below, all you'll need for the Guessing Jar is a large, clear container with a lid (I cleaned out an almond container from Costco for mine), a label for the jar, a folder, and some sticky notes or scraps of paper.
"How many things do you think there are in this little Guessing Jar?"
Each month, decide upon what type of scrumptious treat with which you'd like to fill the jar. Some examples I've used in the past, with the time of year/unit in parenthesis are:
Candy corn/pumpkins (fall)
Apple candy (fall)
Gummy trees (Christmas, temperate rainforest)
Snowman poop/marshmallows (winter)
Gummy snowflakes/snowmen (winter)
Gummy hearts/mixed pink & red candy (St. Valentine's Day)
Golden chocolate coins(St. Patrick's Day)
Gummy butterflies (spring/summer)
Pilot bread/Hardtac (Oregon Trail/Fur Trapper)
Swedish fish (temperate rainforest)
Trail mix, crackers, dried fruit, etc will work year round. Usually, I base it off of what I can get on clearance, in the seasonal bulk candy bins at Winco, or just whatever is least expensive at the store!
Preparing for the Glorious Guessing Jar Day
I love watching which of my students will be the first to realize that I have filled the Guessing Jar with some new form of tasty treat. Initially, you will want to carefully wash your hands, clean/sanitize the container, and add the filling. Screw the lid on tightly and make sure your students know that the lid must stay on the container at all times until it is Guessing Jar Day. Explain to your students that they will be making an estimate (here's a great lesson in and of itself), and cover different strategies for making an accurate estimate. They can pick it up, count the number of treats on the outside, count how many are on one side, etc. Once they have an estimate, they can take a little sticky note/slip of paper, and write their guess, the label, and their name on the paper (such as, "452 candy corn pieces, Mrs. Madison). Let them know that if it is missing any of these three things, it will tragically be thrown away; then you will have to deal with fewer no names. I like to get them in the habit of labeling any mathematical answer, as it will serve them well throughout their math careers. Once they have their guess, label, and name recorded, they can open the folder and add their estimate to their classmates'. There is no peeking into the folder before hand to base their guess off of someone else's estimate; sneaking a peek will also result in their tragic disqualification (they can always try again next month). I usually put this on the morning board as one of their tasks to do as they prepare for the day, which also helps reinforce the importance of following the board directions in the morning.
Guessing Jar Day
In reality, the whole Guessing Jar activity usually only takes about an hour, but you could very easily fill an entire day with it. I save one morning a month to do Guessing Jar, and the kids LOVE it. Here's how the morning goes:
1. Students wipe down their desktop & pencil, wash their hands, get a piece of paper towel at their desk, and get a piece of graph paper out at their desk.
2. While students head and title their papers, I rove around the classroom and hand out a random handful of the Guessing Jar contents to each student on their paper towel when I see they are ready. It doesn't matter how much they get at this point, because we will divide it all evenly later. There is always something for every student to be doing, whether they are a slow worker or fast; this helps ensure their full engagement. If students are not doing their jobs as mathematicians during Guessing Jar, then they do not earn its delicious contents (I have only had this happen once in the last six years).
3. Their first job is to count how many they have (often times I will have them categorize whatever it is by color, shape, etc to add additional dimensions to our data) and to record their results on their graph paper. Then they help their table group find their personal totals, and finally they determine their whole table group totals. Once everyone has it written down, they choose one representative to come up to the Smartboard and record their table's data in our class chart (just a chart with table group names and columns to record each table group's data). Quick students will complete this and have time to find the total number for the whole class, and divide it by the number of students so we know how many each student will get at the end of Guessing Jar.
4. Next, you can tailor the Guessing Jar to whatever form of math you're working on. If you're doing fractions, determine the fractional amount of each color of saltwater taffy, for example. If graphing is your focus, create a pictograph of the different types of Chex party mix, or a bar graph for each color of gummy worm. If you're focus is multiplication and division, analyze the data by finding the mean, median, mode, range, etc. I usually do graphs regardless of our current unit of study so they don't have to wait until the end of the school year to hear all the great vocabulary that comes with the unit, and it's great to practice fine motor skills as well as learning to read & create different tables, charts, graphs, etc for literacy.
5. Have your fastest students order the estimates in the Guessing Jar folder from least to greatest. Once you know the total for the Guessing Jar (when your students find it, thus eliminating the need for you to count everything), you can determine which student made the closest estimate. I usually give that student 2 pioneer dollars (part of our classroom's token economy) and we all congratulate him or her. Generally, I have them share how they came up with their accurate estimate, which can further help other students develop their estimation skills.
6. Last, once the main math part is done and the students have determined how many pieces of the Guessing Jar goodies each person gets, we divide them up. If students have more than they need to fill their Guessing Jar quota, they bring their extras to my desk, and students who I originally gave a tiny handful can come up to my desk to get their missing snacks. Sometimes I check the students' papers before they start enjoying their Guessing Jar loot, and other times I have them just turn their papers in so I can check them later.
7. Clean out the Guessing Jar, recycle or hand back the old estimates, and refill the Guessing Jar with something new so the fun can begin again!
If you have students with any kind of allergy, you will obviously want to check the ingredient list very carefully for whatever you decide to put in the jar. In the past, when I have had students who are allergic to multiple things, I didn't even want to take the risk of causing any kind of a reaction. Instead of handling the food or even being near it, I had them work at my desk, and just do the math part. When they were done with the math, they got an alternative treat that was safe for them to eat. This assures their safety, but still keeps if fun because they get something delicious too. Use your best judgement, and always err on the safe side!
I generally do not give out junk food or candy as prizes in my classroom, and I require all daily snacks to be at least moderately healthy. Because we only do Guessing Jar once a month, it should not have any great impact on the overall health of my students, which is how I can justify them eating a few high fructose corn syrup laced treats. I also invite my students to eat part of their tasty math bounty, and then save the rest for lunch or home. Generally, because the container is relatively small, students only end up with a small handful of sugary goodness anyways. Still, the health of your students should be taken into consideration when choosing your Guessing Jar fillings.
Questions about the Guessing Jar Extravaganza? Leave a comment below! If you have a neat variation you can share with us or an idea on how to make it even better, let us know too. If you would like the Word document that has the label I use on my jar, just leave your email address below so I can send it your way. Comment, share, pass it on, and have fun with your students and the Guessing Jar!