probability question

Question

Suppose that S = {1,2,3,4}, A = {2,3}, B = {3,4}, and C = {1,2}
Furthermore, assume that P(1) = 0.1, P(A) = 0.7, and P(B) = 0.5
Please use no more than 3 significant figures in decimal form. Do not use a percentage

a. Find P(3)
b. Find P(C)
c. Find P((A intersect B)complement)

Answer 1

a) P(3) = P(A∩B)=P(A)+P(B)-P(A∪B) = 0.7+0.5-(1-P(1)) = 0.3

 

b) P(C) = P(1)+P(A∩C) = 0.1+0.4 = 0.5

 

c) 1-P(A∩B) = 1-0.3 = 0.7

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Attn: Drawing a venn diagram can help you to do the problem.