If you wanted to calculate the odds of rolling snake eyes, both dice showing one, with two dice then you would have a total of 36 possible outcomes for two dice. Each die has 6 possible outcomes, so you multiply them together to get the total different possibilities. Of these 36 possible outcomes, only one of those, snake eyes, is the outcome sought after. Therefore, the odds of rolling two dice with the same two numbers showing is 1/36.
After doing these calculations over and over it becomes much easier to calculate these odds in your head quickly. This is one tool that successful gamblers use to help give them an advantage when money is being wagered.
Another industry where odds and probability are used similarly is the insurance industry. Insurance companies use odds and probabilities to calculate their risk, and therefore know how much to charge customers for their policies. Being able to calculate odds easily and quickly will be a great advantage for you in many different areas. Next time you are curious about how often an event will happen try to calculate the odds on your own, and you might be surprised at how quickly you can pick up this valuable skill.