Imagine I have 100 marbles in a bag. Each marble is uniquely labeled. I want to draw 9 marbles out of that bag all at once. I call this a selection. Once I have draw 9 marbles, I put them back. I make 50 such selections (in other words I draw 9 marbles and put them back 50 times).

I need to know the probability of selecting no more than 70% of all marbles during this process. In my mind, this probability as a percentage should be 100% - the probability of selecting 70% or more of the marbles.