Probability is a fundamental concept in mathematics that measures how likely an event is to occur. It is expressed as a number between zero and one, where zero means impossible and one means certain. We can also express probability as a percentage from zero percent to one hundred percent.
Let's look at a simple example: flipping a fair coin. When we flip a coin, there are two equally likely outcomes: heads or tails. The probability of getting heads is one half, or zero point five. Similarly, the probability of getting tails is also one half. Notice that the total probability of all possible outcomes equals one.
Another common example is rolling a six-sided die. A standard die has six faces numbered one through six. Each face has an equal chance of landing face up, so each outcome has a probability of one-sixth, which is approximately zero point one six seven. This demonstrates the principle that when all outcomes are equally likely, each probability equals one divided by the total number of outcomes.
There are three fundamental rules of probability. First, all probabilities must be between zero and one, inclusive. Second, the sum of probabilities for all possible outcomes must equal one. Third, for equally likely outcomes, the probability of an event equals the number of favorable outcomes divided by the total number of possible outcomes. These rules form the foundation of probability theory.
To summarize what we have learned about probability: Probability is a mathematical tool that measures how likely events are to occur. It uses values between zero and one, where zero means impossible and one means certain. For equally likely outcomes, we calculate probability by dividing favorable outcomes by total outcomes. All probabilities must sum to one, and this concept forms the foundation for statistics and informed decision making in many fields.