<p>Does anyone know of a good website to learn about probabilities, I totally forgot how to do them?</p>
<p>you can use sparknotes prep section math 2c.</p>
<p>ways something can happen / total outcomes</p>
<p>I mean the more complex ones with multiple events like, If you flip 10 pennies all at the same time, what is the probability that exactly 3 will come up heads and 7 will come up tails?</p>
<p>don't you do 10 choose 3?
which is 120???
i suggest not worrying about probability, i was like you in nov. i had the test in dec and i knew nothing at all about perms and coms. i study and owrked on those problems, when the test day came, there was like almost no perms and coms. although i ended up with a miserable 780 :(</p>
<p>That's what I thought but the answer was 15/128?? I am actually going to take the SAT 2 Math 1C so probably won't see any, just wanted to know in case. From what I've seen though there was only one permutation/combination question out of all 50 on the practice tests.</p>
<p>As Tiger said, it is chances of success divided by total possible outcomes.</p>
<p>In this case, chances of success are 10!/7!(10-7)! or 120.
Since you have ten coins and two possibilities (tail or head), the total of possible outcomes is (2)^10 or 1024.</p>
<p>The answer is 120/1024 and it reduces to 15/128. </p>
<p>For full details, google Pascal trees or binomial distribution.</p>