this post was submitted on 24 Nov 2024
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2d10 would be used if each arrow had a 10% chance of being cursed. But that's not the case. There are 10 arrows, five are cursed, and 2 are selected. Therefore the first arrow would have a 5/10 chance of being cursed, while the second selection would have either a 4/9 or 5/9 chance of being cursed depending on whether or not the first arrow was cursed.
To solve this, requires using combinatorics. There are 10 choose 2 (45) ways to choose two arrows, of which there are 5 choose 2 (10) ways to choose 2 arrows that are non-cursed. This works out to be 2/9 odds to pull two safe arrows. Which means you need to get funkier with the dice.
If they pulled one, checked if it was cursed, and then pulled another, you'd be right
But they pulled two out of ten at the same time.
So roll two d10s, and say odds are cursed and even would regular. And that's good enough.
I mean, maybe I'm missing something and I didn't spell it out exactly what I meant in the first comment, but that should be the exact same odds as the action.
But what if I roll 2 times 1? I can't pull arrow 1 twice!
Re-roll on a repeat