To help mathematics educators realise the power of computer-based applications and modelling, this paper deals with four questions: (a) What implications does technology have for the range of applications and modelling problems that can be introduced? (b) In what cases does technology facilitate the learning of applications and modelling? (c) When may technology enrich learning possibilities? (d) Can applications and modelling be successfully done without any technology? Answers to these questions are based upon the IBMT (Interaction Between Mathematics and Technology) principle: "When using mathematics, don't forget available tool(s); when utilizing tool, don't forget the underlying mathematics."