# conditional probability

• Mar 1st 2011, 11:31 PM
violette
conditional probability
hi,can anyone pls help.thx!!

a friend randomly chooses 2 cards,without replacement, from an ordinary deck of 52 cards.determine the conditional probability that both cards are aces if you ask your friend if either of the cards selected is an ace and your friend said yes.
• Mar 1st 2011, 11:59 PM
matheagle
are you asking P(both are aces|at least one is an ace)?

If so, just use $P(A|B)={P(AB)\over P(B)}$

Let A=both are aces

B=at least one is an ace

AB=A so P(AB)=P(A)= (4/52)(3/51)

while P(B)=1-P(No aces)=1-(48/52)(47/51)
• Mar 2nd 2011, 12:02 AM
violette
Yups
• Mar 2nd 2011, 12:04 AM
matheagle
done