There are two possibilities, the missing card is a club card or the missing card is not a club card. The probability that the missing card is a club card is ¼, and the probability that it is not a club card is ¾.
Case I: When the missing card is a club card:
The probability that the two cards drawn are club cards = \(\frac{12C_2}{51C_2} = \frac{12\times11}{51\times50}\)
Case II: When the missing card is not a club card:
The probability that the two cards drawn are club cards = \(\frac{13C_2}{51C_2} = \frac{13\times12}{51\times50}\)
By Baye’s Rule,
The required probability = \(\frac{\frac{1}{4}\times\frac{12\times11}{51\times50} }{ \frac{1}{4}\times\frac{12\times11}{51\times50}+\frac{3}{4}\times\frac{13\times12}{51\times50 }}= \frac{11}{50}\)
Hence, option C is the correct option.
A | B | C | D | Average |
---|---|---|---|---|
3 | 4 | 4 | ? | 4 |
3 | ? | 5 | ? | 4 |
? | 3 | 3 | ? | 4 |
? | ? | ? | ? | 4.25 |
4 | 4 | 4 | 4.25 |