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by danjuma » Sat Nov 27, 2010 3:30 pm
A drawer contains 36 stocks and 2 stocks are selected at random without replacement. What is the probability that both socks are black?


1.The probability is 4/9 that the first sock is black.

2.The number of white socks in the drawer is 4 more than the number of black socks.
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by Laura GMAT Tutor » Sat Nov 27, 2010 3:50 pm
Where did you find this question?
Last edited by Laura GMAT Tutor on Sat Nov 27, 2010 4:19 pm, edited 1 time in total.
follow me on twitter! :)
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or visit my blog:
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by kevincanspain » Sat Nov 27, 2010 4:04 pm
danjuma wrote:A drawer contains 36 stocks and 2 stocks are selected at random without replacement. What is the probability that both socks are black?


1.The probability is 4/9 that the first sock is black.

2.The number of white socks in the drawer is 4 more than the number of black socks.
Ask yourself what you need to know in order to answer the question: how many of the 36 socks are black?

(1) tells us that 4/9 of the 36 socks are black. SUFF
(2) tells us that there are at least 4 black socks. However, there may be socks that are neither black nor white NOT SUFF
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