Between 1998 and 2011 there were three reports of studies whose focus was the development of PTs’ knowledgeof decimals(Stacey et al., 2001; 
Widjaja, Stacey, & Steinle, 2008, 2011). Widjaja and her colleagues (2008, 2011) explored the density of rational numbers and the representation of negative decimals to gain insights into misconceptions 
about decimals that might be hidden in more familiar contexts. The work of Stacey at al