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# The probability that a visitor at the mall buys a pack of

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Intern
Joined: 24 Feb 2012
Posts: 31
Re: the prob that a visitor at the mall buys a pack of candy is  [#permalink]

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24 Feb 2012, 12:48
3
6 trials
4 successes w/ prob of each success = 3/10
2 failures w/ prob of each failure = 7/10

6C4 x (3/10)^4 x (7/10)^2
=0.0595
=approximately 6%
Manager
Joined: 24 Dec 2016
Posts: 79
Location: India
Concentration: Finance, General Management
WE: Information Technology (Computer Software)
Re: The probability that a visitor at the mall buys a pack of  [#permalink]

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12 Mar 2017, 05:06
bmwhype2 wrote:
The probability that a visitor at the mall buys a pack of candy is 0.3. If 6 visitors came to the mall today, what is the probability that exactly 4 will buy candy?

$$\frac{6!}{4!*2!}*0.3^4*0.7^2$$

Why do we have to multiply $$\frac{6!}{4!*2!}$$ ?
I don't think the sequence in which people buy matters here. Does it ?

Bunuel, kindly help.
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Joined: 02 Sep 2009
Posts: 47137
Re: The probability that a visitor at the mall buys a pack of  [#permalink]

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12 Mar 2017, 06:22
Shruti0805 wrote:
bmwhype2 wrote:
The probability that a visitor at the mall buys a pack of candy is 0.3. If 6 visitors came to the mall today, what is the probability that exactly 4 will buy candy?

$$\frac{6!}{4!*2!}*0.3^4*0.7^2$$

Why do we have to multiply $$\frac{6!}{4!*2!}$$ ?
I don't think the sequence in which people buy matters here. Does it ?

Bunuel, kindly help.

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Intern
Joined: 16 Nov 2016
Posts: 30
Location: India
GPA: 3.78
WE: Accounting (Accounting)
Re: The probability that a visitor at the mall buys a pack of  [#permalink]

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29 Mar 2017, 19:40
Can someone help me understand why we don't consider the combinations
Therefore p(B)=3/10 p(N)=7/10
3/10^4 * 7/10 ^2 * 6!/4!*2!

Is this also the correct answer??
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Posts: 7304
Re: The probability that a visitor at the mall buys a pack of  [#permalink]

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15 May 2018, 15:07
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Re: The probability that a visitor at the mall buys a pack of &nbs [#permalink] 15 May 2018, 15:07

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