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let's talk about probability in general. there is this website where you can generate private keys on the fly and check their balance (lots of websites like this one actually but I was using a specific one).
so the total number of pages is: 2573157538607026564968244111304175730063056983979442319613448069811514699875

I was randomly typing digits, adding and erasing some when I came across page 257315753860702656496824411130417573006305698397944231
(https://privatekeys.pw/keys/bitcoin/257315753860702656496824411130417573006305698397944231)

there is a private key wallet that had had a transaction in 2018 (now it's empty).
so I did a little math. the average number of transactions in 2020 was 300,000 daily. in 2021 it was 400,000 daily.
before 2020 it was less but lets say it was 200,000 a day. so roughly there was about 73,000,000 transactions a year or 730,000,000 transactions in 10 years.
so by a very rough estimate it was nearly one billion transactions in Bitcoin network over all (I don't have real statistics though I'm pretty sure it exists somewhere).  

now to my question. I'm bad with large numbers. could anyone tell me the probability of randomly finding a private key wallet with transaction given the fact that that 'database' supposed to have 10e +77 private keys and there was only 1 billion transactions and I happen to find one?
or to rephrase it - there are less than 100,000,000 wallets in use and I've randomly found one. what are the chances of that?