Respuesta :
Answer:
a. 19/60
b. 21/26
c. ¼
Step-by-step explanation:
This problem can be solved using the sets language/ notations and rules of probability.
a.
Let probability of traditional painter be written as P(TP) and probability of contemporary painter be written as P(CP)
From the given data:
P(TP) = 2/3
P(CP) = 2/5
P(TP U CP) = ¾ where U represent union of events TP and CP which means at least one of them is commissioned.
The probability of both TP and CP are commissioned can be written as P(TP ∩ CP) where ∩ represents intersection of the two events TP and CP.
Using the rule of probability:
P(AUB) = P(A) + P(B) – P(A∩B)
P(TP U CP) = P(TP) + P(CP) – P(TP ∩ CP)
Substituting the values:
¾ = 2/3 + 2/5 + P(TP ∩ CP)
Rearranging and making P(TP ∩ CP) the subject in the above equation
P(TP ∩ CP) = ¾ - (2/3 + 2/5)
P(TP ∩ CP) = 19/60 (Answer)
b.
It is the question of conditional probability
The rule for conditional probability is that the probability of A conditioned on B, denoted P(A|B), is equal to P(AB)/P(B).
In our case it can be written as P(TP | only one is commissioned) = P(only one is commissioned and TP is the one commissioned) / P(only one is commissioned).
P(only one is commissioned and TP is the one commissioned) = P(TP) – P(both are commissioned)
P(only one is commissioned and TP is the one commissioned) = 2/3 - 19/60
P(only one is commissioned and TP is the one commissioned) = 7/20
Similarly:
P(only one is commissioned and CP is the one commissioned) = 2/5 - 19/60
P(only one is commissioned and CP is the one commissioned) = 1/12
P(only one is commissioned) = P(only one is commissioned and TP is the one commissioned) + P(only one is commissioned and CP is the one commissioned)
P(only one is commissioned) = 7/20 + 1/12
P(only one is commissioned) = 13/30
Therefore:
P(TP | only one is commissioned) = P(only one is commissioned and TP is the one commissioned) / P(only one is commissioned).
P(TP | only one is commissioned) = (7/20) / 13/30
P(TP | only one is commissioned) = 21/26 (Answer)
c.
Using complement rule of probability which is:
P(Neither is commissioned) = 1 – P(at least one is commissioned)
P(TP U CP)’ = 1 - P(TP U CP)
P(TP U CP)’ = 1 – ¾
P(TP U CP) = ¼ (Answer)