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[–] 35 points 9 months ago (6 children)

Oooh! This is a great solution to this problem! Just write down both numbers and perform a luhn check:

https://en.wikipedia.org/wiki/Luhn_algorithm

The one that lies only has a 1 in 10 chance of making up a number that will pass the check! Cool shortcut: If it starts with a 1, 2, 7, 8, or 9, they're lying. Those are reserved for things that aren't credit cards 👍

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  • [–] 19 points 9 months ago (2 children)

    But you only can ask one question and asking for their CC information won't help you find the exit.

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  • [–] 2 points 9 months ago (2 children)

    I thought credit card numbers were just for credit cards, what are the "things that aren't credit cards"? Genuine question I'm just curious.

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