If A and B are two independent events such that =2/15 and
=1/6, then find P(B).
Let ,
denote the complements of A, B respectively.
Given that, P(A∩) )
P(A)P()
P(A)[1–P(B)]
P(A)=1/6[1–P(B)]
P(A'∩B)
P(A')P(B)
[1–P(A)]P(B) )
[1–1/6{1–P(B)}]P(B) )
[{6–6P(B)–1}/{6–6P(B)}]P(B) )
15[5–6P(B)]P(B)=2[6–6P(B)]
15[5–6P(B)]P(B)=12[1–P(B)]
5[5–6P(B)]P(B)=4[1–P(B)]
25P(B)–30[P(B)]2=4–4P(B)
–30[P(B)]2+25P(B)+4P(B)–4=0
30[P(B)]2–29P(B)+4=0
30a2–29a+4=0 where P(B)=a
30a2–24a–5a+4=0
6a(5a–4)–1(5a–4)=0
(6a–1)(5a–4)=0
6a–1=0
6a=1
a
P(B)
5a–4=0
5a=4
a=
P(B)
Therefore, P(B),