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JEE Main 2026 Preparation: Question Papers, Solutions, Mock Tests & Strategy Unacademy » JEE Study Material » Mathematics » Probability of an event

Probability of an event

Types of Events in Probability may be taken off as a set of possible outcomes of an experiment

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Probability is the study of how likely an event is to occur. There are several real-world circumstances in which we may be required to forecast the result of a certain occurrence. First, the outcome of an event might be known with certainty or unknown to us. When this is the case, we say that the event has a chance of occurring or not. Probability is widely used in gaming, industry, and the burgeoning field of artificial intelligence.

The probability formula may be used to determine the likelihood of an occurrence by dividing the favourable number of possibilities by the total number of Simple Events that might occur. This is a simple formula. As long as there are no more positive outcomes than total outcomes, there is no limit to the chance of an event occurring. Furthermore, it is impossible to have a negative figure for the number of successful outcomes. In the next sections, we’ll go through the fundamentals of probability in further depth.

What is Probability?

An event’s probability may be calculated by dividing the number of outcomes by the number of favourable outcomes. X denotes the number of positive results in an experiment with n outcomes. The formula for determining an event’s likelihood is as follows.

Assuming that the outcome is favourable, the probability (Event) equals x/n.

To better grasp probability, let’s look at a basic example. Let’s say we have to make an educated guess about whether or not it will rain today. Either “yes” or “no” is the correct response to this question. Whether it rains or not is up in the air. Probability may be used in this situation. It is possible to anticipate the result of coin tosses, dice rolls, or the drawing of playing cards using probability.

Probability Theory terminology

The following terminology in probability aid in the comprehension of probability concepts.

  • The term “experiment” refers to a test or procedure intended to achieve a result.
  • A sample space is a collection of all possible results of an experiment. Tossing a coin, for instance, generates the outcomes “heads” and “tails.”
  • Outcomes that meet or exceed expectations are referred to as “favourable outcomes.” There are three possible/favourable possibilities of having the total of the two dice as 4 when we roll two dice: (1,3), (2,2) and (4,1),(3,1).
  • A random experiment is referred to as a trial.
  • Random Experiment: A random experiment has a predetermined set of results. However, we can’t guarantee that we’ll obtain either the head or tail when we toss one.
  •  Simple Events is the sum of all possible outcomes in a random experiment.
  • When two or more events cannot occur simultaneously, they’re termed “mutually exclusive.” For instance, it might be either hot or chilly when it comes to temperature. We can’t all be in the same place at the same time and have the same weather.

The Mathematical formula for the probability

The probability formula is used to calculate the chances that a certain event will take place. It’s a measure of how many good things happen compared to all of the bad things that happen. Probability may be summarized using the following formula:

P(A)= No of favourable outcomes in A/No of possible outcomes

where,

For example, the probability of an occurrence known as “A” is P(A).

The formula gives the total number of events that occur in a sample space, n(S).

Determining the Types of Events in Probability of an event

An experiment’s probability of an occurrence measures how likely it will happen. Between (and including) “0” and “1” is the likelihood of each given occurrence.

Probability of occurrences

When it comes to probability theory, an event is a group of outcomes in the sample space or a portion of it.

We have if P(E) indicates the probability of an occurrence E,

It’s only feasible for E to be impossible for P(E) to be zero.

If E is a sure event, P(E) = 1.

When we divide P(E) by P(E), the answer is 1.

Event A has a higher chance than event B only if we are given two occurrences, one of which is “B” and the other is “A”. An experiment’s sample space (S) collects all potential outcomes, and n(S) is the number of possible outcomes. In mathematics, P(E) equals n(E) divided by the number of elements (S)

Assuming that we have the same number of S’s as E’s, we can calculate the P’s by multiplying the number of E’s by S.

The symbol E denotes the absence of the event’.

As a result, we may deduce that P(E) + P(E’) = 1

Probability of a Successful Flip of a Coin

Let’s have a look at the coin-tossing likelihood now. When it comes to choosing who will bowl or bat first in a game like a cricket, coin tossing is often used. First, look at how tossing a single coin may be used to the notion of probability. In addition, we’ll take a closer look at the throwing of two and three coins.

The Coin toss: Mutually Exclusive Events

Tossing a coin yields two possible outcomes: a head or a tail. To calculate the likelihood of obtaining a head or a tail, the idea of probability, which is the ratio of favourable Simple Events to total outcomes, may be applied.

Sample Space = H, T, where H stands for “Head,” and T for “Tail.”

P(H) equals the probability of getting heads.

How many tails/total outcomes is P(T)=1/2?

Two Coins: Compound events

We have a total of four possible outcomes when we throw two coins in the air. The likelihood of getting two heads, one head, or no heads may be computed using the probability formula, as can the probability of getting two tails. Here are the probabilities for each of the two heads.

This experiment yielded a total of four different results, and the sample space was calculated as follows:

P(2H) = Number of outcomes with two heads/Total Outcomes = ¼

Probability of rolling a dice

Many games rely on dice to determine the actions of the players. If you want to know the results of a dice game, you need to understand the notions of probability. Various probabilities for outcomes may be determined when using two dice in several games. Investigate the 

outcomes and odds based on only one die and two dice!

Making a Single Roll of the Dice

When a die is rolled, there are a total of six possible outcomes, and the sample space is 1, 2, 3, 4, 5, 6. To better grasp the idea of probability on a single dice throw, we will calculate the following several probabilities. To calculate the probability of an even number result, you divide the number of outcomes by the total number of outcomes.

The probability of odd number results divided by the total number of outcomes is 3/6 = 1/2. For example, 3/6 = 1/2 is the ratio of prime number outcomes to the total results.

Conclusion: 

Probability states that simple occurrences have a predetermined likelihood of occurring. Today, for example, there’s a 10% chance of rain. When more than one possibility exists, the overall probability is computed by summing the individual probabilities. For example, if there is a 10% probability of snow and a 15% possibility of hail, there is a 25% risk of poor weather. In this post, we learnt how to calculate the likelihood of a basic event that will occur.

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