#probability

16 messages · Page 1 of 1 (latest)

rare fossil
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If we have 2 black and 2 white balls in a box and we need to take 2 balls out, what is the probability that we take 2 black balls?

uncut laurelBOT
grand eagle
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It's without replacement, isn't it?

rare fossil
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I think

grand eagle
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So what is the probability for one black and one white

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In the first drawing

rare fossil
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I have 2 ideas and I don't know which is right

grand eagle
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ok

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tellem

rare fossil
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We can take {BW,WW,BB,WB} than its 1/4, or there are 2 blacks and I want 2 so I can take (2/2) / (4/2) =1/6 ( by that I mean the formula( 2!/2!*0! )... I

grand eagle
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It's the last one

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You first have BBWW ok!

P(B) = 2/4 = 1/2 ok!

Now you take a black one.

You have now BWW

P(B) is now 1/3

You take another black one.

Now you multiply it P(BB) = 1/2 x 1/3 = 1/6

rare fossil
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Okay thanks!

grand eagle
# rare fossil Okay thanks!

P(BB) = 1/4 would be the case with replacement, meaning after you took the black one, you put it back and the pull the next one.

rare fossil
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Okay that makes sence now

grand eagle