Math
posted by Luu Luu on .
Sally has seven blue socks and three white socks in a drawer. She picks out two socks without looking. What is the probability that both socks will be blue?

What is 7/10*6/9 ?

There are choose(10,2) = 45 ways to choose two things from ten if order doesn't matter.
There are choose(7,2) = 21 ways to choose two blue socks.
So 21/45 = 7/15
(This is the same answer as Bob's... do you see why?)