# Probability addition rule

If two dice are thrown, what is the probability that the first die shows a 4 or that the total on the two dice is 8?

So far in calculations:

Event A = 4/36

Event B = 5/36

(4/36 + 5/36) - 1/36 = 8/36 or 2/9 which is not the correct answer.

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If two dice are thrown, what is the probability that the first die shows a 4 or that the total ...

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Probability based on addition rule is discussed in the answer.

Probability : Addition and Multiplication Rules

It can be easy enough to get the addition rule and the multiplication rule confused. Tell me the difference between the two. Provide the notations and then tell me what type of problem I would use each one for.

Addition Rule:

Notation for Addition Rule: P(A or B) = P(event A occurs or event B occurs or they both occur).

Multiplication Rule:

Notation: P(A and B) = P(event A occurs in a first trial and event B occurs in a second trial).