How to Solve Probabilty Problems

Simple calculations can find the probability of any given outcome in a situation.

Calculating the probability of achieving a certain result can help you place a bet or make an educated guess. The basic probability equation is simple and easy to relate to real-life situations; you can create and solve it quickly to determine your chances. With simple counting and a little division and multiplication, you can quickly find your odds or finish your homework assignment.

Instructions

1. Count the number of possible outcomes for the given situation. For example, with a deck of 52 cards, if you were to pull a single card from the deck, there are 52 possible outcomes.

2. Count the number of possible outcomes that contain the desired result. For example, there is only one of each card in a deck, so if you want to pull a specific card, such as the ace of spades, there is only one possible desired outcome.

3. Divide the number of desired outcomes by the number of possible outcomes. For example, if your desired outcome is pulling an ace of spades out of a deck of cards, there is only one possible desired outcome and a total of 52 outcomes. The probability is then 1/52 or .019.

Tips & Warnings

• For probability of a specific set, such as a pair of kings, find the probability of one, then the second, and multiply. Each time you remove an item from the total possible outcomes, subtract from the total for the next item. For example, the first king has a probability of 4/52 because there are four kings per deck, but the second king has a probability of 3/51 -- there are three kings, and 51 total cards, left in the deck. The total probability becomes 4/52 x 3/51 or .0045

References

• MathGoodies: Introduction to Probability

Resources

• MathGoodies: Probability