Probability question


#1

3 boxes practically indistiguishable in appearance have 2 drawers each.box 1 contains a gold coin in first silver coin in the other drawer , box2 contains a gold coin in each drawer and box3 contains a silver coin in each drawer.one box is chosen at random and one of its drawers is copied at random and a gold coin is found.what is the probability that the other drawer contains a coin of silver


#2

Let C1C1 = event that cabinet 1 is chosen

Let C2C2 = event that cabinet 2 is chosen

Let SS = event that a silver coin is chosen

P(C1/S)=P(S/C1)P(C1)/P(S/C1)P(C1)+P(S/C2)P(C2)

P(C1/S)=10.5/10.5+0.5*0.5

P(C1/S)=2/3