GMATPrep - probability w/ cards

This topic has expert replies
Source: — Problem Solving |

Master | Next Rank: 500 Posts
Posts: 127
Joined: Sat Apr 19, 2008 1:02 am
Thanked: 12 times

by jasonc » Fri May 30, 2008 7:25 pm
48-2=46
8/46=4/23

User avatar
Legendary Member
Posts: 566
Joined: Fri Jan 04, 2008 11:01 am
Location: Philadelphia
Thanked: 31 times
GMAT Score:640

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.

Newbie | Next Rank: 10 Posts
Posts: 1
Joined: Mon Jan 07, 2008 5:00 pm

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.

User avatar
Legendary Member
Posts: 566
Joined: Fri Jan 04, 2008 11:01 am
Location: Philadelphia
Thanked: 31 times
GMAT Score:640

by AleksandrM » Sat May 31, 2008 4:36 am
Simple enough. Thanks.