# Probability

How to solve the basic probability problems: definition, examples, and their solutions. (including geometric probability)

## Definition

The probability is

(number of wanted ways) / (number of total ways).

## Example 1

There are 8 ways to select a gray card.

And there are 15 ways to select a card.

So the probability of selecting a gray card is 8/15.

## Example 2

There are 3 ways to select a circle card.

And there are 15 ways to select a card.

So the probability of selecting a circle card is 3/15, 1/5.

## Example 3: Geometric Probability

The total area is 12.

And the colored area is 3.

So the probability of hitting the colored area is 3/12, 1/4.