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The probability that a visitor at the mall buys a pack of candy is 30%

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The probability that a visitor at the mall buys a pack of candy is 30% [#permalink] New post  03 Apr 2011, 16:14
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The probability that a visitor at the mall buys a pack of candy is 30%. If three visitors come to the mall today, what is the probability that exactly two visitors will buy a pack of candy?

A) 0.343
B) 0.147
C) 0.189
D) 0.063
E) 0.027
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subhashghosh
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Re: The probability that a visitor at the mall buys a pack of candy is 30% [#permalink] New post  03 Apr 2011, 17:58
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3C2 * (3/10)^2 * 7/10

= 3 * 9/100 * 7/10

= 189/1000

= 0.189

Answer - C

For such questions, there is the formula I've used above. Please check it in Walker's Probability tutorial.
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Re: The probability that a visitor at the mall buys a pack of candy is 30% [#permalink] New post  03 Apr 2011, 16:45
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__ __ __
.3 .3 .7

__ __ __
.3 .7 .3

__ __ __
.7 .3 .3

probability of exactly 3 people buying it is 3(.3*.3*.7) = .189

Ans C
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CMcAboy
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Re: The probability that a visitor at the mall buys a pack of candy is 30% [#permalink] New post  03 Apr 2011, 18:28
Where can I find Walker's Probability Tutorial?
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Re: The probability that a visitor at the mall buys a pack of candy is 30% [#permalink] New post  03 Apr 2011, 19:15
Here you go :
math-probability-87244.html
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Re: The probability that a visitor at the mall buys a pack of candy is 30% [#permalink] New post  18 Jun 2020, 13:57
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3*(.3*.3*.7)
The order inside the bracket changes three times but the product remains the same

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Eaneru
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Re: The probability that a visitor at the mall buys a pack of candy is 30% [#permalink] New post  28 Jun 2020, 04:06
It is 3C2 x 3/10 x 3/10 x 7/10. 3C2 = the number of ways of choosing 2 of three visitors who will buy. their prob being 3/10 and one person who does not buy = 7/10.
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Re: The probability that a visitor at the mall buys a pack of candy is 30% [#permalink] New post  14 Feb 2021, 21:32
P(buys) = 0.3, P(~buy) = 0.7

P(3 visitors buy) = 0.3 x 0.3 x 0.7 x 3! /2! = 189/1000 = 0.189

We multiply by 3! /2! because there are 3 people that need to be arranged and 2 of them buy.

Answer is C.
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Re: The probability that a visitor at the mall buys a pack of candy is 30% [#permalink] New post  08 Oct 2023, 05:29
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