Question : A bag contains 20 coins. If the probability that bag contains exactly 4 biased coin is 1/3 and that of exactly 5 biased coin is 2/3, then the probability that all the biased coin are sorted out from the bag in exactly 10 draws is
(A) \dfrac{5}{33}\dfrac{16C_{6}}{20C_{q}}+\dfrac{1}{11}\dfrac{15C_{5}}{20C_{9}}
(B) \dfrac{2}{33}\left[ \dfrac{16C_{6}+15C_{5}}{20C_{9}}\right]
(C) \dfrac{5}{33}\dfrac{16C_{7}}{20C_{9}}+\dfrac{1}{11}\dfrac{15_{C_{6}}}{20C_{9}}
(D) none of these
Answer : option (B)
Solution :
