Read this excerpt from "On Becoming an Inventor" by Dean Kamen. From this well-stocked basement came a whole new set of really neat projects. My younger brother, Mitch, and his friends, as well as some of my own friends, would come after school to help. At sixteen I was now a young entrepreneur, paying them for their help. I was surprised by the number of orders I was getting for more and more equipment. Soon I didn't have time to build and design new things. Giving over this work to other kids gave me more time to do what I wanted to do. This went on after school and all summer long.

Kamen's style is

informal; he uses slang to entertain his readers.
informal; his purpose is to inform and entertain the reader with his personal experiences.
formal; he uses complex words and ideas to inform the reader of complicated scientific procedures.
formal; his purpose is to persuade the reader to take part in important scientific inventions.