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probability. Probability of an event. Probability . The PROBABILITY of an event is the ratio of the number of times an event occurs to the number of trials. P (A) = n (A) n (S). Example 1.
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probability Probability of an event
Probability The PROBABILITY of an event is the ratio of the number of times an event occurs to the number of trials. P (A) = n (A) n (S)
Example 1 • There are 45 students in form 4 ceria, of which 25 are girls. A student is selected at random from the class. Find the probability that the selected student is a girl.
Solution: The total number of students = 45 The number of girls = 25 Let A be the event of selecting a girl P (A) = number of girls in form 4 ceria total number of students in form 4 ceria = 25 45 = 5 9
Solution ; • The number of blue marbles = 180 – 100 = 80 • P ( selecting a blue marble ) = 80 100 = 4 9
Conclusion… • Probability of event A, P(A)= num.of times event A occur • number of trials • If A will not occur, then P(A) = 0 • If A occurs in every trial, then P(A) = 1 • In general • P(A) = n(A) • n(S) • n(A) = P(A) x n(S)