Number Talk Activities

Estimation Jar
Providing opportunities for Kindergarten children to make estimates helps them build number sense. Number sense is really a byproduct of playing with numbers and is often referred to as flexible thinking or good intuition about numbers. Challenging students to regularly make estimates enables them to make personal connections with numbers, to understand what they mean, practice with mental math and make comparisons.

Key elements which I include in number talks are : 

• community of learners
• class discussion
• purposeful math problem
• time to work
• open ended teacher questions

I introduce the estimation jar during number talks activity. I show one jar and tell them that it has five marshmallows (a friendly number of course). We count the marshmallows together to make sure that five is the correct number. Then using an identical jar, I ask them to think about how many marshmallows are in the second jar. They discuss it with their partner and then some of them share their thinking and encourage them to talk about how they came up with that number * see this post for sample questions  http://crazyforkindergarten68.blogspot.ca/2013/07/number-talks_4.html

There are many many ways to use estimation jars in your program. Once it has been introduced my Kinders use sticky paper to write their guesses during our activity time. Then later during a transition we talk about the number in different ways. Sometimes we compare, count, use tallies, etc. In the third term, I use different containers to increase the challenge and work with larger numbers. It always provides me with insights into their number sense, strategies and math thinking.
Here is a great site that has videos for teaching reasoning and estimating which includes my key elements. 

http://www.learner.org/series/modules/express/pages/ccmathmod_04.html?pop=yes&pid=913%20