Young and older adults were asked toaccomplish a computational estimation task (i.e. provide approximate sums to two-digit addition problems like 38 + 74) under a short versusa longer presentation duration condition. In a choice condition, participants selected the better strategy more often under a long than undera short presentation duration and after an easier than after a harder problem. In the no-choice condition, influence of presentation durationon strategy execution depended on the preceding problems, as participants showed sequence poorer strategy effects. That is, participantswere slower while executing the poorer than while executing the better strategy on current problems following better strategy problems (butequally fast after poorer strategy problems) only under short presentation duration condition. These findings have important theoreticalimplications, as current assumptions of computational models of strategies cannot explain how problem presentation durations influencestrategy selection and strategy execution.