Why do we need to learn Set theory?
Set theory is important because it is a theory of integers, models of axiom systems, infinite ordinals, and real numbers, all in one unified structure. This allows it to serve as a foundation for all of mathematics, anything you talk about in mathematics can be formalized in set theory naturally and easily, and studying set theory allows you to prove theorems about mathematics itself. The formulation of set theory in the late 19th century motivated the meta mathematics of the 20th century, with all the astonishing results about provability.
Where do you find isolated rectangular supported beam ?
What is probaility and possibility
The possibility of any event is always 1 or 0 i.e. 'yes' or 'no'. If an event is possible, how likely will its occurrence be, under a given situation is probability. Example, When we roll a dice, possibility of it showing up number 5 is 'Yes' (or 1), possibility of showing up number 8 is 'No'(or 0).In a situation where the dice is rolled once, Probabilty of it showing up number 5 is 1/6. So, every event that we consider while finding the probability of occurence of a particular event, is a possible event.