Mathematics anxiety negatively affects performance in simple arithmetic tasks. The experiment reported here explored the role of interactivity in defusing the impact of math anxiety on mental arithmetic. Participants were invited to complete additions presented on paper without using their hands or any artefact; in a second, interactive, condition, the same problems were presented in the form of a set of manipulable tokens. Math anxiety was significantly correlated with mental arithmetic performance only in the static condition. The results of a mediation analysis indicated that the effect of math anxiety on mental arithmetic was mediated by working memory capacity in the static condition; in the interactive condition, math anxiety and working memory did not significantly correlate with performance. Interactivity encouraged the coupling of internal and external resources to create a cognitive system that augmented and transformed working memory capacity, diffusing the resource drain caused by math anxiety.