The additional theorem-
The additional theorem states that if two events A and B are mutually exclusive the probability of the occurrence of either A or B is the sum of the individual probability of A and B.
P (Aor B) = P (A) + P (B)
Example– One head is drawn from a standard pack of 52. What is the probability that it is either a king or a queen?
Solution– There is 4 kings and 4 queens in a pack of 52 cards.
The probability that the card drawn is a king = 4/52
And the probability that the card drawn is a queen = 4/52
Since the events are mutually exclusive events the probability that the card drawn is either king or queen
4/52 +4/52 = 8/52 = 2/13 answer
When events are not mutually exclusive events
P (Aor B) = P (A) + P (B) – P (A and B)
In the example taken the probability of drawing a king or a heart shall be-
P (Heart or king) = P (Heart) +P (King) – P (Heart and king)
4/52 +4/52 -1/52 = 4/13 answer
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