Math Help - Probability Question

1. 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!

2. $\displaystyle\left( {\frac{{70}}{{200}}} \right)\left( {\frac{{69}}{{199}}} \right)$

Do you understand why?

3. $\frac{\left({70 \atop 2}\right)}{\left({200\atop 2}\right)}$

4. Originally Posted by MathoMan
70c2/200c2
@MathoMan
Here is a comment: those two answers are equal.