Read the brief research report on “The Empty Number Line in Dutch Second Grade” (Klein, Beishuizen, and Treffers, 2002) or the journal article entitled “The Empty Number Line: A Useful Tool or Just...

Read the brief research report on “The Empty Number Line in Dutch Second Grade” (Klein, Beishuizen, and Treffers, 2002) or the journal article entitled “The Empty Number Line: A Useful Tool or Just Another Procedure?” (Bobis, 2007). These papers describe the use of a number line with no zero point shown as a computational support for children doing multi digit addition and subtraction. What instructional and psychological reasons do the authors give for using the empty number line as a central model for addition and subtraction?