Re: [Quiz] Answer the Bitcoin question and earn merits! #1
Foundry USA has 30.74% of the bitcoin total global hashrate. If he waits for 10 confirmations, he will have the risk of chain reorg reduced to 5.11%.
Correct! 
Although hosseinimr93 explains the why. To get a more accurate estimate, you would need access to data such as the hash power distribution among mining pools
How can hash power distribution among mining pools affect the final outcome?The chance depends on the fee rate used by your customer. Since the mining pool is dominating, if the fee is nice enough for them to add a single confirmation, others will have almost no choice than to confirm the transactions also as they proceed mining the block.
We assume, as I've written, that your transaction already has 10 confirmations. So the fee rate is irrelevant.c)which is different compared to if someone added a tx in by 835,000
but the malicious pool was already making its own chain since 834,750 but doesnt broadcast it until 835,010
The whitepaper demonstrates that if the attacker has less than that, their chance of building a longer chain (difficulty-wise) becomes tiny exponentially. Therefore, when Foundry will have built from 834,750 to 835,010, the rest will be higher than that. (The exact block number they're likely to be is a great future question, though!)but the malicious pool was already making its own chain since 834,750 but doesnt broadcast it until 835,010