Originally Posted by

**abracadab** Hi,

I'm not a university student (I was, but that was many years ago). Nonetheless, I'm trying to solve a probability puzzle, and this seems like the best place on the Internet to ask for help. The puzzle is as follows:

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N people roll two dice.

After the first roll, half of the people are randomly eliminated, and the

other half get to roll both dice a second time. This continues until all

the people are eliminated. (Thus, N/2 people roll the dice exactly once;

N/4 people roll them exactly twice, N/8 people roll them exactly three

times, etc).

When the process is complete, how many of the N people will have rolled

double sixes at least twice? How many will have rolled double sixes at

least three times?

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Any insights you have would be greatly appreciated. I took probability courses years ago, but I've forgotten a lot of it, and I don't even think that problems like this are anything I ever learned to solve!

Thanks very much.

Abracadab