Wednesday, August 5, 2015

Using ESTIMATION JARS to Build Number Sense

Do you use an estimation jar in your classroom?  It is a fun & interactive way to build number sense. 
At the beginning of the year, I introduce the estimation jar.  I fill it with something like Pom Poms, candy, erasers, bouncy balls, etc., and students guess how many objects are in the jar.  
We discuss what would be a good estimate...Does it look like there are 100 Pom Poms in the jar above?   More or less?  Does it look like there are 5 Pom Poms in the jar?  More or less?  
As the kids make guesses, we reference the Hundreds Chart.   We use a dry erase marker to circle the numbers so they have a visual when they are making estimates.  
For a few weeks, I'm in charge of the estimation jar.  I experiment with the size of the objects inside the jar and how full the jar is.  The most important aspect of building number sense is the DISCUSSION that takes place along with the "guessing."  It is NOT blind, random guessing.  I scaffold students' understanding, and I think aloud as students are making estimates.  The math talk that happens during these few minutes of the day is amazing.  
After a few weeks, it is time for the kids to take it home one by one.  I send home directions inside the jar and encourage students to write the answer on a sticky note inside the jar so they don't forget how many they put in.  I love this activity because it gets parents involved!  Seriously, the kids get SO CREATIVE with the objects they bring in.  My favorite is when the first kid brings in exactly 23 chocolate bars... One for each student and one for ME  :)  
(Example of directions I send inside the jar.  Laminate this page so it can be reused.) 
The same discussion and scaffolding happens as the students take turns with the estimation jar.  It's an activity that we do year round.  The student that has the correct estimate gets to take the jar home.  If they've already had a turn, they get to pick somebody who has not had a turn yet.  

I've done the Estimation Jar at various times throughout the day.  Some years I do it as part of our "Calendar time."  Other years, I do it directly after recess or lunch to get everyone settled.  It's so fun and there is so much learning taking place!  Win-Win!  

Download the directions/Parent Letter for FREE here!  


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