
socks
before the holidays end i thought i might brush up on some light revision and now it seems i'm stuck, i've tried karnough maps and the tree diagram but i can't seem to solve this.
Question:
A drawer contains 30 red socks and 20 blue socks.
If a sock is chosen at random, its colour noted, the sock replaced and a second sock is withdrawn, what is the probability that both socks are red?

Because we have replacement we can treat the events (draws) as independent akin to tossing a coin twice.
P(RR) = [n(red)/n(total)]^2

ah now i see my problem, thanks mate