Posted by **ana** on Thursday, April 21, 2011 at 12:59pm.

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?

- math -
**MathMate**, Thursday, April 21, 2011 at 1:22pm
Ways to get 2 socks out of 18

=(18,2)=18!/(2!(18-2)!)

=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%.

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