Hi guys, I’m just wondering how one knows that palpatine isn’t pulling out the say 4 purple marbles in the first 4, so QB would be 0, or 2 purples before the third and thus 1/5, etc etc. Where in the question does it specify that you’re pulling the first purple marble out at the third or the seventh?
You could - but that’s just one possibility. We are trying to find the overall probability of that happening.