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If the coin is tossed 5 times, what is the probability that

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Eternal Intern
Joined: 07 Jun 2003
Posts: 467
Location: Lone Star State
If the coin is tossed 5 times, what is the probability that [#permalink]

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21 Jul 2003, 17:50
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

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)
Manager
Joined: 08 Apr 2003
Posts: 150

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21 Jul 2003, 18:04
Common Curly you know that...

1. 5C3/2^5

2. 2*3C2*2C1/7C4

Am just lazy to calucate that
Manager
Joined: 07 Jul 2003
Posts: 56

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21 Jul 2003, 19:51
1. (5c3+5c4+1)/32. Evensflow, be careful!!!
SVP
Joined: 03 Feb 2003
Posts: 1604

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21 Jul 2003, 22:53
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
Manager
Joined: 10 Jun 2003
Posts: 210
Location: Maryland

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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!
Manager
Joined: 08 Apr 2003
Posts: 150

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22 Jul 2003, 16:43
RK73 wrote:
1. (5c3+5c4+1)/32. Evensflow, be careful!!!

I failed to notice the word "at least".

It does happen when one solves problem at 4:30 in the morning
Founder
Joined: 04 Dec 2002
Posts: 15148
Location: United States (WA)
GMAT 1: 750 Q49 V42

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23 Jul 2003, 00:40
evensflow wrote:
RK73 wrote:
1. (5c3+5c4+1)/32. Evensflow, be careful!!!

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. Manager Joined: 08 Apr 2003 Posts: 150 Show Tags 23 Jul 2003, 14:16 Hey really.... I heard it was a concession of$100 (exactly half the fees). Could you confirm that for me from GMAC.
23 Jul 2003, 14:16
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