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# conditional probability question HELP watch

1. Help please I'm really confused on this question
I'm trying to find the probability of picking a card that is not a diamond, from a deck of 52, given that it is red ??
how would I do this ??
2. (Original post by fefssdf)
Help please I'm really confused on this question
I'm trying to find the probability of picking a card that is not a diamond, from a deck of 52, given that it is red ??
how would I do this ??
So you want the probability that the card is a heart given that it is red.
The fact that it's given to be red means that there are only 26 cards to worry about, 13 diamonds and 13 hearts.
So you need to pick one of the 13 hearts out of 26 possible cards to choose from. So the chances are 13/26 which is 1/2.
3. (Original post by B_9710)
So you want the probability that the card is a heart given that it is red.
The fact that it's given to be red means that there are only 26 cards to worry about, 13 diamonds and 13 hearts.
So you need to pick one of the 13 hearts out of 26 possible cards to choose from. So the chances are 13/26 which is 1/2.
thank you so if you had to find the probability of picking a jack given that it isn't a diamond then the answer would be 1/13 ??
4. Definiton of conditional probability
as can be thought of as the entire sample space as

So,

There are 26 red cards and 13 of those are diamond.
5. (Original post by fefssdf)
thank you so if you had to find the probability of picking a jack given that it isn't a diamond then the answer would be 1/13 ??
Yes, as you can forget about the diamonds, so there would be 3 jacks out of 39 cards.
6. (Original post by fefssdf)
thank you so if you had to find the probability of picking a jack given that it isn't a diamond then the answer would be 1/13 ??
Not a diamond means it could be any of the other 39 cards that aren't diamonds. There are 13 jacks so there are 13 cards you could pick out of 39 so the chances would be 1/3.
7. (Original post by B_9710)
Not a diamond means it could be any of the other 39 cards that aren't diamonds. There are 13 jacks so there are 13 cards you could pick out of 39 so the chances would be 1/3.
There are 13 jacks?
8. (Original post by NotNotBatman)
There are 13 jacks?
In some decks.
Yes then I think you're right.

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