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GMATPrep - probability w/ cards

Expert replies
Source: — Problem Solving |

by jasonc » Fri May 30, 2008 7:25 pm
48-2=46
8/46=4/23
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by AleksandrM » Fri May 30, 2008 8:12 pm
I see. Can you explain the reasoning behind your answer. I understand why you subtracted the two cards you have already drawn and why you put the new probability over the remaining cards. For some reason, I started calculating probability of the first two cards being drawn and then thought of creating a relationship of that result to the probability of the third card being drawn. Though I must confess, I have not practiced any probability or comb/perm at all.
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by logu » Sat May 31, 2008 1:10 am
Since two cards were drawn initially, number of remaining cards will be 48-2 = 46

Total number of shares of stock = 8.

Probability to select a card which represent a share of stock = No. of cards of shares of stock / total number of cards
= 8/46 = 4/23.
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by AleksandrM » Sat May 31, 2008 4:36 am
Simple enough. Thanks.
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