# Probability Question

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• September 21st 2010, 07:22 AM
juliak
Probability Question
Based on the attached table, what is the probability that if two people are selected at random that they both of them are nonsmoking females

What I did was

(140/200)(90/200)(139/199)(89/199)

but that was incorrect

can someone tell me the accurate way to do this?

thank you!
• September 21st 2010, 07:38 AM
Plato
$\displaystyle\left( {\frac{{70}}{{200}}} \right)\left( {\frac{{69}}{{199}}} \right)$

Do you understand why?
• September 21st 2010, 08:27 AM
MathoMan
$\frac{\left({70 \atop 2}\right)}{\left({200\atop 2}\right)}$
• September 21st 2010, 08:37 AM
Plato
Quote:

Originally Posted by MathoMan
70c2/200c2

@MathoMan
Here is a comment: those two answers are equal.