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Primel – guess a 5 digit prime number – each guess must be a prime

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Re: Primel – guess a 5 digit prime number – each guess must be a prime

#21

Post by emaro »

metalliqaz wrote: post #14

So are people just really good with numbers? I don't know any 5 digit primes nor do I know a way to calculate them on the fly.

I thought the same, but it rejects guesses that are not valid prime numbers. So you'll find some with trial and error. With that it took me only three guesses.

Re: Primel – guess a 5 digit prime number – each guess must be a prime

#22

Post by Maursault »

metalliqaz wrote: post #14

So are people just really good with numbers? I don't know any 5 digit primes nor do I know a way to calculate them on the fly.

You can guess a prime relatively easily given a few attempts, as besides 2 and 5, all other primes will have a 1, 3, 7, or 9 as its least significant digit. So, for starters, you'd never guess a number with any other least significant digit.

Re: Primel – guess a 5 digit prime number – each guess must be a prime

#23

Post by eCa »

tlholaday wrote: post #9
simonlc wrote: post #5

Earlier quoted context omitted.

It's not a 5 digit prime.

0 is a digit. Apparently I have stumbled over an idiom of the prime-enthusiast community.

> 0 is a digit.

It’s not a significant digit[0], though, when it’s leading.

[0] https://en.wikipedia.org/wiki/Significant_figures

Re: Primel – guess a 5 digit prime number – each guess must be a prime

#24

Post by metalliqaz »

eganist wrote: post #17
metalliqaz wrote: post #14

So are people just really good with numbers? I don't know any 5 digit primes nor do I know a way to calculate them on the fly.

I intuited a probably-inaccurate trick with exponentially raising a small prime (e.g 7*7*7etc), doubling the multiple (*2), and subtracting 1 (to get an odd number). That got me two substantially-different primes and narrowed my numbers a lot, which then became guesswork. My guesses in the end: -?--- ?---! ?-??! ?!??! !!!!!

lol this would not help me at all

by the way am I supposed to take some meaning from the italicized '7' or was that just a typo?

Re: Primel – guess a 5 digit prime number – each guess must be a prime

#28

Post by ColinWright »

metalliqaz wrote: post #24
eganist wrote: post #17

Earlier quoted context omitted.

I intuited a probably-inaccurate trick with exponentially raising a small prime (e.g 7*7*7etc), doubling the multiple (*2), and subtracting 1 (to get an odd number). That got me two substantially-different primes and narrowed my numbers a lot, which then became guesswork. My guesses in the end: -?--- ?---! ?-??! ?!??! !!!!!

lol this would not help me at all by the way am I supposed to take some meaning from the italicized '7' or was that just a typo?

He probably had 7x7x7, but with asterisks instead of the "x"s.

Re: Primel – guess a 5 digit prime number – each guess must be a prime

#29

Post by eganist »

ColinWright wrote: post #28
metalliqaz wrote: post #24

Earlier quoted context omitted.

lol this would not help me at all by the way am I supposed to take some meaning from the italicized '7' or was that just a typo?

He probably had 7x7x7, but with asterisks instead of the "x"s.

correct, thanks for the heads up. Fixed

Re: Primel – guess a 5 digit prime number – each guess must be a prime

#30

Post by 07d046 »

I thought coming up with primes would be very challenging, but then my first three guesses were all prime (all I did was pick numbers that ended with odd numbers that weren't five). I got it on the fourth after a few attempts at entering the number - the prime constraint here makes it easier.

There are 8,363 five digit primes. If you limit your guesses to numbers ending in 1, 3, 7, and 9, there is a 23% chance of randomly picking a prime.

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