Here is another example of a simple error of omission that could have been caught if the student had read the essay aloud or given it to a friend to read. The word "of" should be between "calculation" and "the." That one small error makes the entire sentence awkward and confusing. If the instructor has to reread the sentence to try to understand its meaning, the flow of the essay is interrupted. If this happens often enough in the essay, it gives an overall bad impression on what otherwise might be a very good paper in terms of research.
Deciding on a purpose
Even description for description's sake should have a purpose. Is there an important overall impression you wish to convey? A central theme or general point? This is your thesis; organize your essay around it. For example, you might describe your car as your home away from home, full of snack foods, changes of clothing, old issues of the Chico News & Review , textbooks, and your favorite music. Or, you might describe your car as an immaculate, beautiful, pampered woman on whom you lavish attention and money. Just don't describe your car in cold, clinical detail, front to back (or bottom to top, or inside to outside) without having in mind the purpose, the overall impression you want to create. To achieve this impression, you should not necessarily include all details; use only those that suit your purpose.