Did you do an aptitude test for this competition? If so, was part of it a case study? If yes, your presentation will be based on this.
If not, you will probably be given a scenario in case study format and asked to prepare a presentation on this. It is usually the case that you are given two options, you choose one and give a presentation on it.
In any event there is no need for Powerpoint, it will simply be flipchart and markers. As with any presentation, it is not how flashy your slides are, it is your presentation skills and information being imparted that count. You won't be expected to give the presentation for 45 minutes on the issue either. Usually it is ten or fifteen minutes and you will then be quizzed as to why you said this, that or the other in the presentation.