You are given a sack containing $n$ red balls and $n$ blue balls. You take the balls out of the sack one by one and write down the sequence of reds and blues you get. How many sequences are possible?
Tell me more
×
Mathematics Stack Exchange is a question and answer site for
people studying math at any level and professionals in related fields. It's 100% free, no registration required.
|
|
|
HINT: A sequence is completely determined by the position in it of the $n$ red balls: once you know where they are, you also know where the blue balls are. How many different sets of $n$ positions are there in a string of $2n$ positions? |
|||||
|
