[Note that probability of occcurrence.of.A is same whether B occurs or does notoccurs ⇒ A and B are independent] P (A ∩ B) [1 - P(B)] = P(B) P(A) - P(B) . P(A ∩ B) P(A ∩ B) = P(A) . P(B) ⇒ true
P(W) =
w
w+d
.
w+d
w+d+b
+
b
b+w
.
w
w+b+d
=
w
(b+w)(w+b+d)
(w + d + b)
w
w+b
Hence the probability that 2nd ball drawn is white is independent of d. (d) Every key that fits have the same probability =