This presentation introduces a new – and easy to implement – proximity coefficient 𝑃3for quantifying the degree of interleaving. Firth et al. (2021) contrasted interleaving andblock study to each other where the latter is to focus only one learning goal during asequence of exercises while interleaving means to intertwine different learning goals.Organising the order of exercises for students according to interleaving or block studyhas different consequences for students’ learning. In a post-test, Noh et al. (2016) foundthat when students had practiced according to interleaving, they achieved better on tasksthat required the students to integrate information. On the other hand, they also foundthat when students had practiced according to block-study, they achieved better on tasksthat required rule-based skills. Interleaving is relevant not only for the mathematicalcontent, but also for how the content is represented, namely, Rau et al. (2013) found thatstudents achieved better when the lesson design was to present learning goals asinterleaving and representations as block-study when compared to the opposite designof their classroom experiment.