The Conditional probability formula states that 'the probability of A given event B is'
[tex]P(A|B)=\frac{P(A\cap B)}{P(B)}[/tex]Therefore, in our case, the probability of a marble being odd given that it is blue is
[tex]P(odd|blue)=\frac{P(odd\cap blue)}{P(blue)}=\frac{\frac{9}{11+18}}{\frac{18}{11+18}}[/tex]Simplifying,
[tex]\Rightarrow P(odd|blue)=\frac{9}{18}=\frac{1}{2}[/tex]Thus, the probability the marble is odd given that it is blue is 1/2. The answer is 1/2.
