Alaundry basket contains 18 blue socks and 24 black socks. what is the probability of randomly picking 2 black socks from the basket?

Altogether there are 42 socks in the basket.  Since there are 18 blue socks, the probability of picking a blue sock on the first draw is 18/42.  What is the prob. of picking a black sock on the first draw?

Now suppose that the first sock drawn is black.  Take that sock out of the basket.  This leaves 23 black socks.  Figure out the probability that the next sock drawn will also be black.  Note:  the total number of socks is now 41, not 42.

Finally, mult. these 2 probabilities together.  Why?