Question : An unbiased cubic die marked with 1, 2, 2, 3, 3, 3 is rolled 3 times. The probability of getting a total score of 4 or 6 is
(A) 16/216
(B) 50/216
(C) 60/216
(D) none of these
Answer : option (B)
Solution :
Die marked with 1, 2, 2, 3, 3, 3 is throw 3 times
P(1) = 1/6, P(2) = 2/6, P(3) = 3/6
P(S) = P(4 or 6)
= P(112 (3 cases) or 123 (6 cases) or 222)
=\ 3\times \dfrac{1}{6}\times \dfrac{1}{6}\times \dfrac{2}{6}+6\times \dfrac{1}{6}\times \dfrac{2}{6}\times \dfrac{3}{6}+\dfrac{2}{6}\times \dfrac{2}{6}\times \dfrac{2}{6}
=\dfrac{6+36+8}{216}=\dfrac{50}{216}