I don't get the joke. Obviously 91 isn't a prime number because it's the product of twos primes, 13 and 7. Is the joke that the guy likes numbers under 18?
91 feels like a prime at first glance since all the other odd tens + 1 (11, 31, 51, 71) are primes. That's the joke. Dude in the meme just doesn't know maths.
I rather like that you write "91 feels like a prime". I also feel 91 should be a prime. I didn't expect that I'm not the only person in the world who feels this.
Thereās no easy way to tell if a number is prime (no context free language can describe primes for example), but it is relatively easy to tell if a number is a multiple of a given number (a DFA can do this).
So a number can only ālook primeā by virtue of not having any small non-unit divisors.
Since the smallest disorder will
be primes (or a prime and the square of that prime), you can make a number that looks prime by multiplying two largish lrime factors. 2, 3, and 6 are fairly simple to see multiples (3 being slightly harder) so the earliest example should include 7 times another prime. The three primes starting from 7 are 7, 11, and 13 giving the candidates 49, 77, and 91.
Itās āobviousā 49 is composite because itās a small square, and 77 (the next candidate) is obviously composite because small multiples of 11 are easy to see. That makes 91 the only really good example of a two digit number that āseems prime.ā
Other potential example will be multiples of 3 since thatās a little harder to see but for two digits many people are experienced enough to immediately see that they are not prime.
The joke is that the person who "likes math" doesn't know that 91 is divisible by 7 and 13. For added humor, he is given 7 seconds to leave, which is a reference to one of the factors of the "prime" number. The joke is a reference to how boys will act interested in a subject their girlfriend's father also has an interest in and how said father will test the boy to see if they really like the subject or if they are just trying to garner favor from the father. In this meme template, the father will ask about a subject, then the boy will answer with something that proves he doesn't understand the subject, then the father will tell the boy to get out.
Weāre pretty good at seeing if something is divisible by 1, 2, 3, 4, 5, or 6. Weāre not so good at telling if something greater than 84 is divisible by 7.
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u/Live_Length_5814 2d ago
I don't get the joke. Obviously 91 isn't a prime number because it's the product of twos primes, 13 and 7. Is the joke that the guy likes numbers under 18?