probability

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Odissia: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Mon Oct 01, 2007 12:08 pm; Location: Chicago

by Odissia » Thu Oct 04, 2007 5:43 pm

Hi everybody,

here is one question:
Three cards are chosen at rendom from a desk without replacement. what is the probability of getting a jack, a tan and a nine in order?

1. 8\16575
2. 1\2197
3. 6\35152
4. none of the above

Thanks

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Source: Beat The GMAT — Problem Solving | Thu Oct 04, 2007 5:43 pm

Leonard C: Junior | Next Rank: 30 Posts; Posts: 28; Joined: Mon Jul 16, 2007 7:29 amFollowed by: 1 member; Thanked: 8 times

by Leonard C » Sun Oct 07, 2007 2:32 am

You can do this simply by:

(4/52) x (4/51) x (4/50) = 8/16,575.

You start with 52 cards, but since there is no replacement, your sample population decreases by one.

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sonibubu: Junior | Next Rank: 30 Posts; Posts: 21; Joined: Fri Sep 21, 2007 6:43 am

by sonibubu » Thu Oct 11, 2007 8:13 am

I agree with Leonard. The whole "tan" thing threw me off, I was wondering if there are tan colored cards

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joshi.komal: Senior | Next Rank: 100 Posts; Posts: 74; Joined: Tue Sep 25, 2007 7:58 am; Thanked: 4 times

by joshi.komal » Sun Oct 14, 2007 7:59 am

Well..even I am scared of probability

But Now I have started getting the feel about it.

The best way when you get such problems where you are taking out something and not putting back then the number at the bottom will decrease by one which is your sample space. In this case it is the total no of cards or you may even have balls in a bag.

Next is how many jacks out of the total are there in the deck it is 4 so your probability for the first time will be: you will get any 4 out of total 52.
So probability of getting jack is 4/52.
now you have to ppick ten but the number of cards have reduced by 1.
So probability will 4 out 51 i.e 4/51.

Similarly the next will Nine 4/50.

so the total probability will be a product of these.

4/52*4/51*4/50

Thanks
Komal

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Odissia: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Mon Oct 01, 2007 12:08 pm; Location: Chicago

good job!

by Odissia » Sun Oct 14, 2007 11:45 am

they are really good explanations! Thanks for all of you.
I downlowded some materials from this web site about probability which are very helpful.

Odissia.

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