In order to teach a conceptual understanding of problems and their solution procedures as
well as to facilitate schema induction, worked-out examples have been proven more
effective than simply presenting abstract principles or having learners solve problems on
their own (Atkinson et al. 2000). Worked-out examples consist of a problem statement
(e.g., a word problem) and a step-by-step solution procedure, where the application of the
latter to the former is illustrated and explained. In order to help learners extract the relevant
structural features of problems, it has been proven useful to not only provide single
examples, but example combinations.