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Help with math problem XD
Topic Started: Nov 4 2005, 11:46 PM (142 Views)
lord_carbo
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Note: I'm not sure if this belongs in Brain Juice or not. It's probably an easy problem to anyone who isn't dumb like me :P

I need help with something. We are going to learn probabilities in math class. Although I pretty much know the fundamentals of probabilities, I've been ever so stumped with this that I brought up while daydreaming during science class...

Quote:
 
If I have 10 black marbles and 10 white marbles, what are the odds that if I draw 3 marbles one at a time (and NOT put them back in the bag), what are the odds of at least two of them being white?


Well, the odds of drawing all three being white is 10/20*9/19*8/18 (I think XD), but what about if I only wanted two of them to be white? I've fiddled around but I just can't find anything.

No, this isn't homework help XD I've just been fussing over this and I'm going crazy and I just want to move on >_>

Also, please explain how you did it so I can do this universally >_<
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4th Down
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I'm not good at Math! I'm getting a bad grade= 99.5%
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lord_carbo
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4th Down
Nov 5 2005, 03:50 AM
I'm not good at Math! I'm getting a bad grade= 99.5%

Oh my, 99.5%. I envy you.
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.Chris
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Oh hell. Probabilities.... I never got them when we did it in 7th grade and I haven't used them since and I'm in advanced Algebra-II.

Are you sure you have the question down right. Because if to draw three, wouldn't it just be 3/20 if there was no specific color?

---> Probability <_< <---- Me
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convergent
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These kind of topics aren't allowed here at the SZ.
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Monty-Po
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I believe its 3/20

Anyways, dont you have the book?

I dont know if im right, since its been a while since Ive done that.

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rivulet
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.Mercenary
Nov 4 2005, 11:52 PM
These kind of topics aren't allowed here at the SZ.

Actually, since it's not a homework question, as he stated, it is allowed.
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esjay
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i got 50% chance

Combinations are:
WWW
WWB
WBW
WBB
BWW
BWB
BBW
BBB

oh and you're right but you have to add the others as well

(10/20 * 9/19 * 8/18) + (10/20 * 9/19 * 10/18) + (10/20 * 10/19 * 9/18) + (10/20 * 10/19 * 9/18) = 2/19 + 5/38 + 5/38 + 5/38 = 1/2

Which is what I got anyway. I used the tracking diagram
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Typhoon2
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4th Down
Nov 5 2005, 03:50 AM
I'm not good at Math! I'm getting a bad grade= 99.5%

Oh God! That is low!
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