Basic Probability Formulas

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Basic probability formulas are the formulas used while answering questions related to probability. Probability is one of the topics in mathematics which revolves around finding the chances of occurrence of an event. If A is an event, then probability of occurrence of event A happening is usually represented as P(A). Probability of a certain event is always between ‘0’ and ‘1’, where ‘0’ represents no chance of that event happening.
 

Example 1: A six faced dice is thrown. Find the probability of number three not occurring on dice. 

Given that a six faced dice is thrown.

For every single dice there are 6 possibilities i.e. {1,2,3,4,5,6}

The probability of number 3 occurring on one dice is 1/6.

According to Probability formula: Sum of all possibilities is = 1.

Hence, the probability that number 3 does not occur is 1- 1/6 = 5/6.
 

Example 2:Two six faced dice are thrown one after the other. Find the probability of number 1 not occurring on either of the dices. 

Given two six faced dice are thrown.

Each dice has 6 possibilities i.e. {1,2,3,4,5,6}

The probability of number 1 occurring on one dice is 1/6.

According to Probability formula: Sum of all possibilities is = 1.

The probability that number 1 does not occur for the first dice is 1- 1/6 = 5/6.

Therefore even for the second dice probability of 1 not occurring is 5/6.

Hence probability of 1 not occurring for both the dice is 5/6 * 5/6 = 25/36.




 

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