Math Tool Tip & Missing Addend Activity

Just wanted to share a great tip for organizing a math tool many of us use with students, Unifix cubes.  While taking a math workshop recently, the presenter suggested not only putting Unifix cubes in groups of ten (which many of us already do), but she also suggested using two different colors to show groups of five (see picture below).  The reason for this is quite simple, but one I had never thought of.  A second grader may choose Unifix cubes to represent a "situation", but when he/she has to count them individually he/she is reverting back to an earlier stage of development that is not necessary.  By organizing cubes in this way, a student can easily see five and add on. In this way, showing a value such as 12 becomes much more appropriate and efficient.

Here's a great missing addend activity that was shared in the same workshop! Students work in partners.  All that is needed is a group of ten Unifix cubes organized as shown above.  One partner holds the ten Unifix cubes behind his/her back.  Then he/she makes a break and shows his/her partner one group while keeping the other group behind his/her back.  The other partner must then tell how many cubes are hidden. He/she must also "prove" it by counting up or back or by stating what he/she knows.  See the photo and example below.

A student might respond, "You are showing me six cubes, and I know there are ten.  Six plus four equals ten, so four are hiding."
I hope you find these items useful!