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# A three-person committee must be chosen from a group of 7

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VP
Joined: 30 Jun 2008
Posts: 1034
A three-person committee must be chosen from a group of 7 [#permalink]

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18 Sep 2008, 09:54
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100% (02:38) correct 0% (00:00) wrong based on 1 sessions

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A three-person committee must be chosen from a group of 7 professors and 10 graduate students. What is the probability that the committee has at least one professor ?

No OA
_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

Director
Joined: 12 Jul 2008
Posts: 515
Schools: Wharton

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18 Sep 2008, 10:06
amitdgr wrote:
A three-person committee must be chosen from a group of 7 professors and 10 graduate students. What is the probability that the committee has at least one professor ?

No OA

Total number of ways to choose 3 from 17 = 17C3 = 680
Total number of ways to choose a group of only grad students = 10C3 = 120

Probability = (680-120)/680 = 14/17
VP
Joined: 30 Jun 2008
Posts: 1034

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18 Sep 2008, 10:12
zoinnk wrote:
amitdgr wrote:
A three-person committee must be chosen from a group of 7 professors and 10 graduate students. What is the probability that the committee has at least one professor ?

No OA

Total number of ways to choose 3 from 17 = 17C3 = 680
Total number of ways to choose a group of only grad students = 10C3 = 120

Probability = (680-120)/680 = 14/17

680-120 is to determine the cases where we have at least one prof ?
_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

VP
Joined: 30 Jun 2008
Posts: 1034

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18 Sep 2008, 10:13
How to solve this one zoinnk ?

The probability that it will rain in NYC on any given day in July is 30%. what is the probability that it will rain on exactly 3 days from July 5 to July 10 ?

a. 1
b. 1/2
c. 1/3
d. 1/8
e. 1/70
_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

Director
Joined: 12 Jul 2008
Posts: 515
Schools: Wharton

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18 Sep 2008, 10:33
amitdgr wrote:
How to solve this one zoinnk ?

The probability that it will rain in NYC on any given day in July is 30%. what is the probability that it will rain on exactly 3 days from July 5 to July 10 ?

a. 1
b. 1/2
c. 1/3
d. 1/8
e. 1/70

I can't get to any of your choices --

(.3)^3*(.7)^3*(6C3) = .18522
VP
Joined: 30 Jun 2008
Posts: 1034

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18 Sep 2008, 10:37
zoinnk wrote:
amitdgr wrote:
How to solve this one zoinnk ?

The probability that it will rain in NYC on any given day in July is 30%. what is the probability that it will rain on exactly 3 days from July 5 to July 10 ?

a. 1
b. 1/2
c. 1/3
d. 1/8
e. 1/70

I can't get to any of your choices --

(.3)^3*(.7)^3*(6C3) = .18522

I guess I got the choices wrong.

_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

Director
Joined: 12 Jul 2008
Posts: 515
Schools: Wharton

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18 Sep 2008, 10:47
1
KUDOS
amitdgr wrote:
zoinnk wrote:
amitdgr wrote:
How to solve this one zoinnk ?

The probability that it will rain in NYC on any given day in July is 30%. what is the probability that it will rain on exactly 3 days from July 5 to July 10 ?

a. 1
b. 1/2
c. 1/3
d. 1/8
e. 1/70

I can't get to any of your choices --

(.3)^3*(.7)^3*(6C3) = .18522

I guess I got the choices wrong.

Ian Stewart has a nice explanation here:
http://www.beatthegmat.com/probability- ... 14715.html
VP
Joined: 30 Jun 2008
Posts: 1034

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18 Sep 2008, 10:54
zoinnk wrote:
Ian Stewart has a nice explanation here:
http://www.beatthegmat.com/probability- ... 14715.html

+1 for you
_________________

"You have to find it. No one else can find it for you." - Bjorn Borg

Re: PS: Probability   [#permalink] 18 Sep 2008, 10:54
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