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I have chronic indecisiveness. Often times at restaurants, I am presented with 10s of food options, all of which seem pretty much the same to me.

My go-to solution for this problem is to simply order what somebody else is ordering, or ask for the waiter to do it for me, and so on. Occasionally I will use a random number generator on my phone.

I have thought about an RNG that only requires your brain to work, but couldn’t come up with anything. Even TIME % n is just too hard.

Do you know of a way to quickly randomly choose from a small range of number 0<n<~20, using nothing but your brain, or whatever else you can find around you?

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    Binary search guided by coin flips. No coin? Count something mod 2. Characters in a printed sentence, ceiling tiles, whatever. Entropy is everywhere, you just need to look outside your brain.

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      I think you probably need something like a Linear Congruential Generator. This will give you a reasonable psuedo random number with a bit of calcuation. In an LCG, the next value is (a * <last value> + c) mod m.

      I suggest that to make it easy, you choose 5 for a, 1 for c and 16 for m. So you multiply your last value (or if you forgot it, some other relatively random number, like adding the digits of the minute together) by 5, add 1, then keep taking away 16 until you get a value less than 16.

      Multiplying by 5 is easy mentally (times by ten, then half), and adding 1 is easy, so the only difficult part is the mod 16. Since the maximum result before the modulus is 76, you shouldn’t ever have to subtract by 16 more than 4 times, or alternatively learning the first 4 numbers of the 16 times table is very doable.

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        Dices?

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          Do you know of a way to quickly randomly choose from a small range of number 0<n<~20, using nothing but your brain, or whatever else you can find around you?

          I use an app for that since I’ll have my phone on me when I’m out.

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            Have a coffee first (or drink if it’s that sort of situation).

            Then look for the specialty of the house. ie. What the chef is rightly proud of. When I first read of this tip, the example was “Herrings”, but at a price point that seemed high for such a simple thing. What was served was a grand platter of every sort of herring.

            And definitely ask the waitress what she recommends. She’s not just an automaton, treat her as a person of value with knowledge and valued opinions, who you are pleased to served by and appreciate her time, and guess what, when you do so, all those things are true.

            Much much better than an RNG any day!