Guess-timation Jars

Today was the first day with the kids returning with our new math-ideas estimation jars. I wish I could say where I heard about the idea. It may have even been on Pinterest. I modified this activity to add to our daily math routine. It is a great way to encourage communication and math-talk. We estimate, make predictions, talk about the objects in the jar.  The discussion revolving around the jar and the items can easily be student or teacher led, and can serve as a great transition during your math time.

Here's how it works. Two students each get to take home an estimation jar (I bought these at the dollar store). They can fill it with any amount of 1 object (ex. 5 blocks, 20 pennies, 10 lollipops). Smaller numbers below 50 make it easier to count and compare. The kids return the next day with their jars and I display it on my desk - far enough away that they won't be able to count the items specifically.

At the end of our math-number routine I take out the jars. We discuss the items inside, and the estimation jar leaders tell the group why they chose those items. We compare jars and ask questions like:  How many items do you estimate are in this jar? Are there more that 10? Less than 20? Which jar holds more? etc.

This takes place at the calendar wall where I have number-lines, whiteboard, and other manipulatives on hand for visual reinforcement.  We sit whole-group and take a few minutes to draw conclusions and edit our thoughts - then we count the items.

The first day I modeled the estimation jars I had 11 small tiles in one jar, and 10 larger blocks in the other. When I asked them which jar they thought held more, the immediately pointed to the blocks - likely because they were bigger items and nearly filled the jar. When we counted them during the reveal, they learned that there were more tiles than blocks. We also discussed that just because something is bigger and may fill the jar, it doesn't necessarily mean there are more.

The kids love it so far - and so do I!