The stories of this type are referred to as Equalize. Also, in this case, there are three problems associated with each story.
* Type of story: Compare, Equalize, Change, and Change-Compare
Of the 39 problems that we have considered, 9 are of the class Change, 6 of Equalize, 6 of Compare and 18 of Change-Compare.
A research study was carried out among several groups of students to contrast Change-Compare problems with Change, Equalize and Compare problems, and to establish the influence of the expression of the variation and the difference, as well as the effect of the problem characteristics.
T1: Change 5, Change-Compare 2.1, Change-Compare 5.5, Change-Compare 5.6, Equalize 5, Compare 5.
Problems Change 5, Change-Compare 5.5 and Change-Compare 5.6 only differ in the expression of the Variation; analogously, with Equalize 5 and Compare 5 problems.
As shown in Table 5, the two problems, Equalize 6 and Equalize 1, with the unknown as referent, do not have low success rates.
In order to confirm our idea concerning the importance of the expression, we have taken four classes of additive problems with positive numbers, three of which (Change, Compare and Equalize) were previously quite well-known, and the fourth class (Change-Compare) has been investigated in our research for the very first time.
So, it can be said that the IR-characteristic is a particularly negative condition with Change-Compare problems but of less consequence in Compare or Equalize problems.