Number Stretch:

While student teaching, this manipulative was created using sentence strips in order for my students to visualize the connection between the standard and extended form of numbers.  By showing students how the number "stretches" in the extended form, they made the connection that each digit has a specific value within the number.  Additionally, the written form of the number was written on the back of the strip as well. 

This strip was created in order for students to self correct their answers: