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Eternal Intern
Joined: 07 Jun 2003
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If the coin is tossed 5 times, what is the probability that [#permalink]
 21 Jul 2003, 17:50
If the coin is tossed 5 times, what is the probability that at least 3 out of 5 times it will show heads? (Binominal Distribution)
There are 2 green, 3 red, and 2 blue balls in a box. 4 are drawn at random without replacement. What is the probability that of the 4 drawn balls two are red, 1 is green, and 1 is blue? (Hypergeometric Distribution)
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Manager
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Common Curly you know that...
1. 5C3/2^5
2. 2*3C2*2C1/7C4
Am just lazy to calucate that 
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Manager
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1. (5c3+5c4+1)/32. Evensflow, be careful!!!
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SVP
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RK73 wrote: 1. (5c3+5c4+1)/32. Evensflow, be careful!!!
Agree, be careful
AT LEAST 3 out of 5, not exactly 3 out of 5
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Manager
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With Calculations.. [#permalink]
22 Jul 2003, 07:02
So with calculations (since we will need to do this on the actual test - the more practice now the better!!)
1) 5C3/32 + 5C4/32 + 1/32 = 16/32 = 1/2
Makes sense because the possible numbers of heads are: 0,1,2,3,4 or 5.
Considering the cases 3,4, and 5, we have half of those cases so the prob is 1/2.
2) (2C1 * 3C2 * 2C1)/7C4 = 2*3*2/35 = 12/35
Hope that would be one of the answer choices on the test!
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Manager
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RK73 wrote: 1. (5c3+5c4+1)/32. Evensflow, be careful!!!
My bad....
I failed to notice the word " at least".
It does happen when one solves problem at 4:30 in the morning
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Founder
Status: On Vacation :-)
Affiliations: UA-1K, SPG-G, HH-D
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evensflow wrote: RK73 wrote: 1. (5c3+5c4+1)/32. Evensflow, be careful!!! My bad.... I failed to notice the word " at least". It does happen when one solves problem at 4:30 in the morning I thought I was a maniac....
Are you planning to sign up for the GMAT at 4 AM?
I heard you can get $20 off if you take your test before 6 AM. 
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Manager
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Hey really.... I heard it was a concession of $100 (exactly half the fees). Could you confirm that for me from GMAC.
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