The structure of the card number varies by system. For example, American Express card numbers start with 37; Carte Blanche and Diners Club with 38. American Express - Digits three and four are type and currency, digits five through 11 are the account number, digits 12 through 14 are the card number within the account and digit 15 is a check digit.
The model is the most basic element of the scientific method. Everything done in science is done with models. A model is any simplification, substitute or stand-in for what you are actually studying or trying to predict. Models are used because they are convenient substitutes, the way that a recipe is a convenient aid in cooking.
How science workspage 2 of 21 previous | next. The real process of science. The process of science, as represented here, is the opposite of cookbook (to see the full complexity of the process, roll your mouse over each element). In contrast to the linear steps of the simplified scientific method, this process is non-linear: If you can't see or operate the above interactive item, you can try to get the Flash player or view a static version of the interactive content. 1  The process of science is iterative.