math
posted by ana on .
a draw holds 5 navy socks, 7 white socks and 6 black socks. if two socks are selected at random without looking what is the probability that they do no match?

Ways to get 2 socks out of 18
=(18,2)=18!/(2!(182)!)
=153
Ways to get 2 navy socks
=(5,2)
Ways to get 2 white socks
=(7,2)
Ways to get 2 black socks
=(6,2)
So ways to get two different coloured socks
=(153(5,2)(6,2)7,2))
out of a total possible 153 ways.
Calculate the probability.
I get less than 70%.