The document explains the probability of the event A or B in the context of tossing a coin three times, where A and B are defined sets of outcomes. It calculates the probabilities for each event, stating that P(A ∪ B) is equal to P(A) + P(B) - P(A ∩ B). The author also offers private or group tutoring services with contact information included.

1. Maths topic for
Probability:
probability of
the event A OR B
By Dhruv Sethi;
dhrsethi1@gmail.com/+91 9310805977
11th Grade

2. Probability of the Event A OR B
Let A = {HHT, HTH, THH} and B = {HTH, THH, HHH} be two events associated with
‘tossing of a coin thrice’.
A U B = {HHT, HTH, THH, HHH}
P(A U B) = P(HHT) + P(HTH) + P(THH) + P(HHH)
If all outcomes are equally likely then,
P(A U B) = 1/8 + 1/8 + 1/8 + 1/8 = 4/8 = ½
Also P(A) = P(HHT) + P(HTH) + P(THH) = 3/8
P(B) = P(HTH) + P(THH) + P(HHH) = 3/8

3. Probability of the Event A OR B
P(A U B) ≠ P(A) + P(B) but rather P(A U B) = P(A) + P(B) – P(A ∩ B)
where A ∩ B = {HTH, THH}.
Therefore P(A ∩ B) = 1/8 + 1/8 = 2/8 = ¼
Thus P(A U B) = P(A) + P(B) – P(A ∩ B)

4. Probability of the Event A OR B
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