How many slides you need for your presentation depends. There is no standard rule like one slide per 5 minutes. It depends. Maybe you don’t need any slides. In most cases you will need fewer
slides that you originally think. It is important to think about how many slides you really need to support your presentation. Although you can use your slides as a memory aid to ensure you cover
what you want to say, but in principle the slides are there for your audience and not for you. In the book that is part of the Public Speaking Kit you will find
a lot of great tips and trick about how to effectively use slides as part of your presentation.