# exactly, and at least : Probability

thanks for looking at my question. Any help would be appreciated!

at a university 60% of the students are male and 40% are female

If ten students are selected at random, what is the probability that we have exactly seven females?

and

What is the probability of selecting at least seven females?

a simple explanation would be greatly appreciated, i just cant seem to figure this one out. Thanks!

Hint: It is fairly simple to calculate what the probability of selecting exactly $i$ females for any value of $i$ is. Take a look at the binomial distribution.
• Try and calculate the probability that exactly $7$ females will be selected. Then, the probabilitz that exactly $8$ will be selected and so on. Sum them all to get the probability of selecting at least $7$. – 5xum Mar 31 '14 at 7:39
• You forgot the binomial coefficients. If an event has a chance of happening of $p$, then it will happen $k$ times in $n$ attempts with the probability ${n\choose k}p^k(1-p)^{n-k}$, not only $p^k(1-p)^{n-k}$. – 5xum Mar 31 '14 at 9:49
• If you are having trouble with notation, $$\dbinom{n}{k} = {{_n}C_k}$$ – InterstellarProbe Jul 19 at 13:03