Missed the lesson, and now i'm blank.
A and B are independent.
P(A) = 0.3
P(A u B) = 0.58
Show that P(B) = 0.4
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so i've got to : 0.28 = P(B) - P(a n b)
so i need to divide 0.28 by 0.7 to get the answer, but i cant see how i'm gonna get the 0.7.
Help if you can, thank you :-)
Pathomaniac
Favorite Answer
P(A u B) = P(A) + P(B) - P(A n B)
P (A u B) = P(A) + P(B) - P(A)P(B)
P(A u B) = P(A) + P(B)(1 - P(A))
P(B) =[ P(A u B) - P(A) ] / [ ( 1 - P(A)) ]
P(B) = ( .58 - .3 ) / ( 1 - .3)
P(B) = .28 / .7
P(B) = .4
?
P(A U B) = P(A) + P(B) - P(A n B)
As they are independent, P(A n B) = P(A) * P(B)
so 0.58 = 0.3 + P(B) - (0.3*PB)
so 0.28 = P(B) - 0.3PB
now just simply factorize the P(B)
0.28 = P(B) (1 - 0.3)
0.28 = P(B) * 0.7
0.4 = P(B)