Multiple-step arithmetic problems can be solved by diverse strategies depending on the mental representation constructed by individuals from the situation described in the text of the problem. This representation will indeed determine the organization of sub-goals to be reached or in other words the order of completion of calculations. This study aims at determining the conditions under which specific strategies are set up by adults. Using a paradigm that allows us to assess when calculations are performed, we show that adults usually organize their sub-goals as they are explicitly mentioned in the problem, even though a strategy that is less demanding on working memory could have been used. However, we show that increasing the difficulty of the problem leads individuals to set up more economic strategies. Moreover, these economic strategies are even more likely to be used when the cognitive cost of the construction of the representation they rely on is low.