How to calculate the probability that something will happen

Probability is a statistical measure that shows the probability of something happening . You can hear examples of probability on a daily basis, such as a meteorologist describing a 75 percent chance of rain, or a news anchor citing one at 10 million odds of winning the lottery. The probability of an event occurring is a fraction or a percentage between 0 and 1 . An event that is guaranteed to happen has a probability of 1. An event that can not happen.

one

Determine the number of possible favorable outcomes in an event, which are the results for which you want to know the probability that it will occur. For example, the number of possible favorable results of drawing an even number, with a roll of a six-sided die is 3 - you can draw a 2, 4 or 6.

two

Determine the total number of possible outcomes for the event . For example, there are six possible numbers that could roll with a roll of a die, because a die has six faces.

3

Write the number of possible favorable results as a numerator, and the total number of possible outcomes as the denominator. In the example, write 3 in the numerator and 6 in the denominator, which is equal to the 06/03 ratio.

4

Reduce the relation to its minimum expression to find the greatest common divisor, which is the largest number that uniformly divides the numerator and the denominator. In the example, 3 is the greatest common divisor that divides exactly 3 and 6.

5

Divide the numerator and the denominator by the greatest common divisor to reach its minimum expression. This gives 3 divided by 3, which equals 1, and 6 divided by 3, which equals 2. This makes the ratio of 1/2, which means that it has a 1 in 2 probability of drawing an even number with a roll of a die.

• You can convert the result into a percentage by dividing the numerator by the denominator, which is 1 divided by 2. This equals 0.5 or 50 percent.
• This example applies only to an event in which all possible outcomes have the same probability of occurring, and only one favorable result can occur at a time.