Tangible refers to things we can see and feel whereas intangible are things that cannot be seen or felt. Let us understand this by an example. Suppose the cost of doing an MBA course from a top business schools is $100000 while the cost of a low rung school is $50000.
Economists use complex numbers in order to make profit predictions. When analyzing business cycles, complex numbers can also come into play. Complex numbers may also help an economist trying to determine the internal rate of return, such as the yield on a bond, or an economic duration.
Here is another category where some other of the number classifications will fit. Real numbers include natural numbers, whole numbers, integers, rational numbers and irrational numbers. Real numbers also include fraction and decimal numbers. In summary, this is a basic overview of the number classification system, as you move to advanced math, you will encounter complex numbers.