!#7# Concepts of probability - Addition Rule & Rule of multiplication

!±8± Concepts of probability - Addition Rule & Rule of multiplication

Most students can, where addition and multiplication rule, the rule is likely to be confusing in use. This article gives a clear vision of where you add and multiply the odds.

A student solves the following two problems here:
Problem: A boy is allowed to select a random number between the numbers 1 to 999. What is the probability that the registered number is divisible by 3 or 5, but not both?

First, we want to know how many numbersdivisible by 3. And 'only (999 / 3 = 333).
More likely that the registered number is divisible by 3 = 333/999 = 1 / 3
Secondly, we discover how many numbers divisible by 5. And 'only (999 / 5 = 199).
More likely that the registered number divisible by 5 = 199 / 999
The probability that the registered number is divisible by 3 or 5, but not both = 1 / 3 +199 / 999 = 532/999. --------------- Adding principle

Problem: A coin and dice are thrown simultaneously. What is the probability that heHead and three at a time?

The probability of obtaining a head = ½
The probability of three = 1 / 6
The probability of three heads = 1 / 2 x 6.1 = 12.1 ------------ principle of multiplication.

Let us know because it has use beyond the first principle Multiplication principle in the problem and the second problem?

The approach depends on the nature of the relationship of events:

Events ------------------------ ratio principle be used
Mutually exclusiveEvents ---------------------- principle added
Independent events ---------------------------- principle of multiplication

Mutually exclusive: Suppose that A and B are two events, and should be mutually exclusive, if B does not occur when an audit and vice versa.

Independent events: Suppose that A and B are two events, and must be independent if the output of an event A does not affect the results of the event B and vice versa.

While the first problem is a case of mutualexclusive events, for example, the number is divisible by which he collected 3 or 5, but not both, used alongside principle.

The second problem is that as an independent event of a roll of the dice and flip a coin, are the events that are independent of each other, using the principle of multiplication.