# Probability – Formula, Calculating

Updated on January 14, 2024

At Brighterly, we are passionate about making mathematics accessible, engaging, and understandable for children. One such engaging topic is probability – a concept that unlocks a whole new perspective to understanding the world around us. This concept goes beyond the realm of textbooks, helping us predict everything from weather forecasts to the outcomes of a football game. But how do we calculate probability? What are the formulas that make sense of this seemingly abstract concept? In this blog post, we’ll dive deep into the world of probability, unraveling its concepts, properties, and methodologies to make this exciting topic easy and fun for children!

## Probability – Definition with Examples

Probability can be an exciting concept to explore, especially when we start to understand its role in our daily lives. It is the mathematical way of expressing how likely or unlikely something is to happen. For instance, when you flip a coin, the probability of landing heads or tails is 50% each, or when you roll a dice, the probability of landing a specific number (say, 3) is one out of six (1/6).

While these examples give an idea of probability, it’s much more than that! Probability pervades in various fields, from predicting weather conditions to forecasting stock market trends.

## What is Probability?

The definition of probability relates to the chances or likelihood of an event occurring. In mathematical terms, probability is a measure of the number of desired outcomes in a set of all possible outcomes. It can range from 0 to 1, where 0 indicates the event will not happen, 1 suggests the event is certain, and any value between them expresses the likelihood of the event happening.

## Definition of an Event in Probability

An event in probability is a specific outcome or combination of outcomes from a random process or experiment. For instance, getting a 6 when rolling a dice or picking a red card from a deck of cards. Events can be as simple as these examples, or much more complex, depending on the situation.

## Definition of Sample Space

The sample space is the set of all possible outcomes of an experiment. For example, if you’re rolling a six-sided die, the sample space is {1, 2, 3, 4, 5, 6}. If you’re flipping a coin, the sample space would be {Heads, Tails}. The sample space is vital in probability as it forms the basis of determining how likely an event is to happen.

## Properties of Probability

Probability has certain properties that help us understand and calculate it better. These properties include:

- The probability of an impossible event is 0.
- The probability of a certain event is 1.
- The probability of an event E, denoted by P(E), lies between 0 and 1 (inclusive).
- The sum of probabilities of all outcomes in the sample space is 1.
- If E1, E2, E3,… are mutually exclusive events (cannot occur simultaneously), then the probability of occurrence of at least one of them is the sum of their individual probabilities.

## Probability of Single Events

The probability of single events is calculated by taking the number of ways an event can occur and dividing it by the number of total outcomes. For example, the probability of drawing an Ace from a deck of 52 cards is 4 (number of Aces) divided by 52 (total cards), which gives a probability of approximately 0.077.

## Probability of Multiple Events

Multiple events in probability refer to the occurrence of more than one outcome. For example, the probability of drawing a red card or an Ace from a deck. We calculate this using the addition or multiplication rule depending on whether the events are mutually exclusive (cannot occur at the same time) or independent (one event doesn’t affect the other).

## Difference Between Theoretical and Experimental Probability

In the world of probability, we often encounter two main types: theoretical probability and experimental probability. Theoretical probability is what we expect to happen, based on mathematical calculations, while experimental probability is what actually happens when we perform an experiment or observe an event. These two types may not always match due to randomness and individual variations in the experiments.

## Formulas in Probability

There are several formulas in probability that are widely used, such as:

- The probability of an event E happening, P(E) = Number of favorable outcomes / Total number of outcomes
- The probability of two independent events E and F happening, P(E and F) = P(E) * P(F)
- The probability of either event E or event F happening, P(E or F) = P(E) + P(F) – P(E and F)

## Calculating Probability – Single Events

Calculating probability for single events is a straightforward process. Let’s take an example of rolling a die. What’s the probability of getting a 4? Since there’s only one 4 on a die, and six possible outcomes, the probability would be 1/6, or approximately 0.167.

## Calculating Probability – Multiple Events

Calculating probability for multiple events can be a bit more complex. Let’s consider drawing a card from a deck. What’s the probability of drawing a red card or an Ace? There are 26 red cards and 4 Aces in a deck, making 30 favorable outcomes. But we’ve counted red Aces twice, so we subtract the 2 red Aces. So the total is 28, and the probability would be 28/52, or 0.538.

## Practice Problems on Probability

To help you better understand probability, we’ve compiled a few practice problems on probability. Try them out, check your answers, and keep learning!

- What’s the probability of getting a tails when you flip a coin?
- If you roll a dice, what’s the probability of getting a number greater than 4?
- From a deck of 52 cards, what’s the probability of drawing a face card (King, Queen, Jack)?

## Conclusion

And there you have it – a complete walkthrough of probability! From its basic definition to complex calculations involving multiple events, we’ve explored the fascinating world of probability together. Here at Brighterly, we believe that understanding such mathematical concepts can be both fun and insightful. It helps us interpret our everyday experiences and phenomena around us. Remember, practice is the key when it comes to mastering probability. So, apply these concepts, experiment with them, and don’t forget to try out the practice problems we shared above. Stay curious, keep learning, and make your journey with mathematics brighter with Brighterly!

## Frequently Asked Questions on Probability

### What is the relationship between odds and probability?

Odds and probability both refer to how likely an event is to occur, but they do so in slightly different ways. Probability is the ratio of the number of ways an event can occur to the total number of possible outcomes, while odds are a comparison of the number of ways an event can occur to the number of ways it can not occur. For example, the probability of drawing an Ace from a deck of 52 cards is 4/52 (or 1/13), whereas the odds are 4:48 (or 1:12).

### Can a probability be negative?

No, a probability cannot be negative. By definition, probability is a measure of how likely an event is to occur, and it ranges from 0 (the event will not happen) to 1 (the event will definitely happen). A negative probability would not make sense in this context, as it would imply less than no chance of the event occurring, which is not possible.

### Why do we need to learn about probability?

Probability is an essential concept in mathematics and life because it allows us to measure and predict outcomes. It is used in a wide range of areas including, but not limited to, statistics, finance, gambling, weather forecasting, risk assessment in insurance and medical tests, and even in everyday decision-making. Understanding probability helps us make informed decisions, analyze data, and understand the world around us.