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probability-candy

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probability-candy

by vscid » Sun Mar 14, 2010 2:50 pm
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?

* 0.343
* 0.147
* 0.189
* 0.063
* 0.027
The GMAT is indeed adaptable. Whenever I answer RC, it proficiently 'adapts' itself to mark my 'right' answer 'wrong'.
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by godspeed » Sun Mar 14, 2010 3:02 pm
Well the answer should be .189

There are be 3 cases here ( for exactly 2 people to buy the candy)

1. Buy-Buy-DoesNotBuy or .3*.3*.7
2.Buy-DoesNotBuy-Buy or .3*.7*.3
3.DoesNotBuy-Buy-Buy or .7*.3*.3

In all these 3 cases there will be exactly 2 vistors buying the candy) So the total probability will be sum of these three which is .189
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