0247: "Factoring the Time"
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 warriorness
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0247: "Factoring the Time"
Alt text: I occasionally do this with mile markers on the highway.
When I was in seventh grade, my math teacher had our class "warmup" by making equations out of the date. For example, if the date were 3/14/02, a solution could be "3+14 = 0*2".
It was 2001 in the fall semester, and eventually somebody realized that since all the dates ended in "01" they could just take the first couple of numbers, do whatever they wanted with them, raise it to the 0 power and set it equal to 1. A rule against doing that was made very quickly, and alternative solutions had to be found.
I still do this very frequently. For example, just today (!) I figured that for all the days this month in the interval [10, 19], you could just take logbase4 of 1 (which is zero btw), and use the zero from the year in multiplication so you'd have 0=0.
(1453, by the way, is prime.)
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yy2bggggs, on Fischer Random chess wrote:Hmmm.... I wonder how how a hypermodern approach would work
 Locus Cosecant
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 thefiddler
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EvanED wrote:Given that the clock displays hours in 24 hour time (as evidenced by the 14:53), I'm going to assume that it is 2:53 am in the comic. I thus have a suggestion for Mr. "I have nothing to do" Stick Figure: sleep!
2:53am = 02:53
2:53pm = 14:53.
I do not do this ever. I would get lost halfway and end up curled up in the foetal position, rocking back and forth, yelling "Make the numbers stop!" It is for the best.
EDIT: I should probably take less time writing my posts That whole thing was explained while I was still pondering (read: playing KOL).
thanks for ten seconds of distraction...
#!/bin/csh
#
set i=0
set limit=2400
while ( $i < $limit )
factor $i
@ i = $i + 1
end
ok back to lab work...
You could write an awk script if you want to use sexagesimal...
#
set i=0
set limit=2400
while ( $i < $limit )
factor $i
@ i = $i + 1
end
ok back to lab work...
You could write an awk script if you want to use sexagesimal...
 JuliaGlass
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I can safely say I've never had any sort of fascination with prime numbers. I play number and word games, but they have little mathematical merit.
Sometimes it feels like I don't really have a language and everything is just a frantic translation. I'm always translating words into numbers and numbers into music and music into pictures and pictures into words and so on without actually latching on to one method of expression.
Sometimes it feels like I don't really have a language and everything is just a frantic translation. I'm always translating words into numbers and numbers into music and music into pictures and pictures into words and so on without actually latching on to one method of expression.
 Twasbrillig
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Re: "Factoring the time" Discussion
warriorness wrote:(1453, by the way, is prime.)
GKJEASFJASFJET!!!
Thanks for ruining what I was totally going to be all smug about.
I cannot believe... just, gah!
I wanted to claim that!
I want to have Bakemaster's babies. It's possible, with science.
I wonder if you can see...
...what is wrong with my signature?
I wonder if you can see...
...what is wrong with my signature?
wing wrote:I'm sorry... But that was THE funniest thing I've ever read on the interbutts.

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 asliceofpi
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prime numbers game
When I was little, we played a game with prime numbers. We called it ping pong. First, you would assign ping and pong a prime number. We used ping=2, pong=3. Then you would start counting starting with one. But instead of saying 2 or any factor of 2, you would say ping.
For instance:
1, ping (2), pong (3), ping (4), 5, ping pong (6), 7 and so on so only the prime numbers would be said as numbers.
Anyways, this is what I do when I'm bored.
For instance:
1, ping (2), pong (3), ping (4), 5, ping pong (6), 7 and so on so only the prime numbers would be said as numbers.
Anyways, this is what I do when I'm bored.
Re: "Factoring the time" Discussion
xkcd wrote:[
Alt text: I occasionally do this with mile markers on the highway.
I use the mile markers to either a) try to see how accurately I can count off seconds by matching my counting with the vehicle's speed or b) see how close of an approximation I can make to the vehicle's actual speed by judging the mile markers. Or I just listen to the radio like a normal human being, but there's no pizazz in that.
I think the alt text should warn the reader not to attempt to factor 1453, as it is prime. Wasted effort, but good for a chuckle. That's what I get for not reading the forum first.
(Come to think of it, it still would have been a wasted effort even if I had been able to factor it. Such is the pointlessness of recreational math.)
(Come to think of it, it still would have been a wasted effort even if I had been able to factor it. Such is the pointlessness of recreational math.)
 skeptical scientist
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Is there any way to figure out 1453 is prime in less than a minute without resorting to a calculator? I figured it wasn't divisible by any prime less than 13, and then decided it was probably prime, but it seems pretty much impossible to see it's prime in your head.
I'm looking forward to the day when the SNES emulator on my computer works by emulating the elementary particles in an actual, physical box with Nintendo stamped on the side.
"With math, all things are possible." —Rebecca Watson
"With math, all things are possible." —Rebecca Watson

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 skeptical scientist
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Well, it's something that can be done with a bit of exercise.
First of all, it is obvious that 1453 is a prime number for humoristic purpose. However, to factor a number in my head, I usually use the following strategy:
1) Get an approximation of the square root of the number. In this case, it is a bit under 40, so 37 is the highest potential factor of the number.
2) There are rules to figure out if a number is divisible by certain factors for numbers up to at least 100, but I doubt you know many. If you do, feel free to use them, but they are no necessity.
3) Don't try to divide the number by each possible factor. Instead, first try to figure out if it is divisible before calculating the exact outcome of the division. This means that if you are trying to figure out if m is divisible by n, you can add or substract multiples of n to m as you please, and divide m by any factor that might come in handy. If you end up with a multiple of n at the end, the original number is divisible by n, so you can now do an exact calculation.
Example: To figure out if 1453 is divisible by 17, first add 17 so you have 1470. Divide by 10 => 147. Substract 17 => 130. Divide by 10 => 13, which is obviously not a multiple of 17.
I'm aware this is likely not the fastest or most efficient way to do it, but it's something most people should be able to do in their head without special training, as long as you can remember one or two numbers while doing mental calculations. With a bit of training, it should be possible to factor most times within a minute.
First of all, it is obvious that 1453 is a prime number for humoristic purpose. However, to factor a number in my head, I usually use the following strategy:
1) Get an approximation of the square root of the number. In this case, it is a bit under 40, so 37 is the highest potential factor of the number.
2) There are rules to figure out if a number is divisible by certain factors for numbers up to at least 100, but I doubt you know many. If you do, feel free to use them, but they are no necessity.
3) Don't try to divide the number by each possible factor. Instead, first try to figure out if it is divisible before calculating the exact outcome of the division. This means that if you are trying to figure out if m is divisible by n, you can add or substract multiples of n to m as you please, and divide m by any factor that might come in handy. If you end up with a multiple of n at the end, the original number is divisible by n, so you can now do an exact calculation.
Example: To figure out if 1453 is divisible by 17, first add 17 so you have 1470. Divide by 10 => 147. Substract 17 => 130. Divide by 10 => 13, which is obviously not a multiple of 17.
I'm aware this is likely not the fastest or most efficient way to do it, but it's something most people should be able to do in their head without special training, as long as you can remember one or two numbers while doing mental calculations. With a bit of training, it should be possible to factor most times within a minute.
 evilbeanfiend
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 macronencer
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I really enjoyed this one! Thanks.
Way back in my teen years (that's around the early 1980s) I had a ZX Spectrum computer. I wrote a prime factorizer for it, and the first number I entered was my phone number (in those days, in that location, it was six digits: 678479).
Turns out 678479 is prime. That spooked me a little, at the time. The first number I tried :\
Way back in my teen years (that's around the early 1980s) I had a ZX Spectrum computer. I wrote a prime factorizer for it, and the first number I entered was my phone number (in those days, in that location, it was six digits: 678479).
Turns out 678479 is prime. That spooked me a little, at the time. The first number I tried :\
I think those are crocodile tears: you must be in de Nile.
Way back when at swim practice (before we had to memorize the squares of numbers through 30 for one of my math classes, so computing the square actually took a nontrivial amount of time), rather than just keeping track of what number length/thing of the set we were on I'd square the number. So when one of the people in my lane would ask what number we were on I'd say the square. No one really got it.
Factoring for the hell of it, though...never really been something I've done.
Factoring for the hell of it, though...never really been something I've done.
Last edited by tloicto on Wed Apr 11, 2007 10:53 am UTC, edited 1 time in total.
 apricity
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engine wrote:The guy working at the computer should definitely be wearing the hat.
"The" hat.
It's out of dress code at work.
I would *totally* be that guy at the computer though. Factorguy is smart and all, but computerguy is cunning. Much cooler.
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it takes just a little practice to learn to be
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 cmacis
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When I wrote a program to find primes (sieve of Erastrones, up to square root), and then wrote a program to read the output files line by line since they got too large for notepad, I was gutted to see that I was so close to being born on a prime year. I was so close to pi day that my birthday counts as a pi approximation (using american date format mm/dd)
li te'o te'a vei pai pi'i ka'o ve'o su'i pa du li no
Mathematician is a function mapping tea onto theorems. Sadly this function is irreversible.
QED is Latin for small empty box.
Ceci nâ€™est pas une [s]pipe[/s] signature.
Mathematician is a function mapping tea onto theorems. Sadly this function is irreversible.
QED is Latin for small empty box.
Ceci nâ€™est pas une [s]pipe[/s] signature.
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