The Probability of a Single Event Occurring
Suppose that an event A can happen in m ways out of a total of n equally likely ways. The probability P(A) of A occurring is defined as:
Let's say one wants to determine the probability of choosing an Ace from a randomly shuffled deck of cards. We know that there are 4 four Aces in the deck. We also know that there are 52 cards in the deck. Therefore, we can say that the probability P(A) of selecting one of the four Aces from the 52 card deck is P(A) = m/n = 4/52 = 0.07692307692308