This is studying for my final, not homework.
Six balls are dropped at random into ten boxes. What is the probability that no box will contain two or more balls?
So I know that to select 6 balls from ten we do: ${10\choose 6}$, but I'm not sure how to check whether or not each box contains less than two balls. Is it just:
${6\choose 1}\over{10\choose 6}$