Suppose that you and a friend are playing cards and decide to make a bet. If your friend draws two face cards, where a face card is a Jack, a Queen, or a King, in succession from a standard deck of 52 cards without replacing the first card, you give him $40. Otherwise, he pays you $10. What is the expected value of your bet? Round your answer to the nearest cent, if necessary.

Respuesta :

Given:

The total number of face cards is 12.

The total number of cards is 52.

The probability of 2 successive face cards is,

[tex]\begin{gathered} \frac{12\times11}{52\times51}=\frac{11}{13\times17} \\ =\frac{11}{221} \end{gathered}[/tex]

The probability of not getting 2 face cards is,

[tex]\begin{gathered} P(\bar{E})=1-P(E) \\ =1-\frac{11}{221} \\ =\frac{210}{221} \end{gathered}[/tex]

Next, to find the expected value.

[tex]\begin{gathered} \frac{11}{221}\times(-40)+\frac{210}{221}(10)=-\frac{440}{221}+\frac{2100}{221} \\ =\text{ \$}7.51 \end{gathered}[/tex]

Hence, the expected value of the bet is $7.51.