em777
Aug 6, 2009, 04:17 PM
Two cards are drawn from a regular deck of 52 cards, without replacement. What is the probability that the first card is an ace of clubs and the second is black?
any one know the answer?
stevetcg
Aug 6, 2009, 04:28 PM
Think it through. The chance of the ace of clubs is 1:52. The subsequent draw is 25:51 (26 black cards minus the ace of clubs).
Add the probabilities together (basic probability math... )
galactus
Aug 6, 2009, 04:45 PM
Sorry Stevetcg, but we should multiply them. If we add them, we get a 53% probability. Intuitively, that does not seem correct.
The multiplication rule of probability, P(A \;\ and \;\ B)=P(A)\cdot P(B|A)
Because the card is not replaced, the events are dependent.
(\frac{1}{52})(\frac{25}{51})
If the problem said, "what is the probability the first card is an ace or black?", then the addition rule would be appropriate.
The word to look for is OR when using Addition.