Is this Prime?
March 18, 2016 11:15 AM Subscribe
The Is this prime? game tests you as you sort numbers into prime and non-prime. Click Yes or No or type Y or N on the keyboard. Uses JavaScript.
The game ends at the first incorrect guess or when the clock runs out. The time, maximum number, and difficulty can be set by clicking the S at the top left.
Stats of previous games here.
The game ends at the first incorrect guess or when the clock runs out. The time, maximum number, and difficulty can be set by clicking the S at the top left.
Stats of previous games here.
I did fine on the first run -- 18 correct -- but for some reason I got tense and my score plummeted to 0-2 on a couple of subsequent runs. Arg. Too much coffee.
posted by Mogur at 11:19 AM on March 18, 2016
posted by Mogur at 11:19 AM on March 18, 2016
8675309
posted by You Can't Tip a Buick at 11:26 AM on March 18, 2016 [3 favorites]
posted by You Can't Tip a Buick at 11:26 AM on March 18, 2016 [3 favorites]
Apparently I sort of enjoy failure.
posted by A Terrible Llama at 11:32 AM on March 18, 2016 [2 favorites]
posted by A Terrible Llama at 11:32 AM on March 18, 2016 [2 favorites]
The first one I got was 1 and then I relived a bunch of high school conversations
posted by beerperson at 11:40 AM on March 18, 2016 [15 favorites]
posted by beerperson at 11:40 AM on March 18, 2016 [15 favorites]
Sieve what I did there.
posted by RobotVoodooPower at 11:40 AM on March 18, 2016 [6 favorites]
posted by RobotVoodooPower at 11:40 AM on March 18, 2016 [6 favorites]
I've gotten tripped up by 57 about three times now.
posted by Betelgeuse at 11:48 AM on March 18, 2016 [7 favorites]
posted by Betelgeuse at 11:48 AM on March 18, 2016 [7 favorites]
The highest I've gotten is 27 so far.
posted by peacheater at 11:51 AM on March 18, 2016
posted by peacheater at 11:51 AM on March 18, 2016
Also my nemesis is 111 (which is stupid since I know the divisibility test for 3).
posted by peacheater at 11:52 AM on March 18, 2016
posted by peacheater at 11:52 AM on March 18, 2016
91 is a lot tougher though - 7 times 13. No divisibility tests there.
posted by peacheater at 11:53 AM on March 18, 2016 [2 favorites]
posted by peacheater at 11:53 AM on March 18, 2016 [2 favorites]
I need to learn my 17 and 19 times tables.
brb
posted by ceiriog at 11:55 AM on March 18, 2016 [4 favorites]
brb
posted by ceiriog at 11:55 AM on March 18, 2016 [4 favorites]
Yeah, 91 got me too.
Also there are so many numbers on the screen at the same time that I'm having trouble focusing on the one I'm supposed to be looking at, making me lose more time, and then the time-panic sets in and aaaaaaaaaaaaa
I did much better at puppy or bagel.
posted by Mchelly at 11:55 AM on March 18, 2016 [1 favorite]
Also there are so many numbers on the screen at the same time that I'm having trouble focusing on the one I'm supposed to be looking at, making me lose more time, and then the time-panic sets in and aaaaaaaaaaaaa
I did much better at puppy or bagel.
posted by Mchelly at 11:55 AM on March 18, 2016 [1 favorite]
Up to 37 now! This is the perfect game for someone who spent her time as a kid on long car rides running divisibility tests on all the license plate numbers.
posted by peacheater at 11:56 AM on March 18, 2016 [7 favorites]
posted by peacheater at 11:56 AM on March 18, 2016 [7 favorites]
I've gotten tripped up by 57 about three times now.
In fairness, though, 57 is incredibly primey.
posted by The Bellman at 12:01 PM on March 18, 2016 [9 favorites]
In fairness, though, 57 is incredibly primey.
posted by The Bellman at 12:01 PM on March 18, 2016 [9 favorites]
Oh man, there goes my wife's evening. (anecdote: she spent several weeks agonizing over if our new home address was prime or not before looking it up. she was right, it was prime. some kind of low grade prime number synethstesia.)
posted by Xyanthilous P. Harrierstick at 12:15 PM on March 18, 2016 [2 favorites]
posted by Xyanthilous P. Harrierstick at 12:15 PM on March 18, 2016 [2 favorites]
I don't care what this site says, Hot Rod will never be a Prime.
posted by Sangermaine at 12:19 PM on March 18, 2016
posted by Sangermaine at 12:19 PM on March 18, 2016
I've gotten tripped up by 57 about three times now.
In fairness, though, 57 is incredibly primey.
and Grothendieck approved. PDF link
posted by yeolcoatl at 12:28 PM on March 18, 2016 [7 favorites]
In fairness, though, 57 is incredibly primey.
and Grothendieck approved. PDF link
posted by yeolcoatl at 12:28 PM on March 18, 2016 [7 favorites]
Ugh. OK: 57, 87, 91, and 117 are all non-primes. Write those down.
OK, back again, got up to 40 when time ran out.
That was remarkably satisfying.
posted by PandaMomentum at 12:29 PM on March 18, 2016
OK, back again, got up to 40 when time ran out.
That was remarkably satisfying.
posted by PandaMomentum at 12:29 PM on March 18, 2016
HA! Apparently 57 is the "Grothendieck Prime," named after French mathematician Alexander Grothendieck:
In a mathematical conversation, someone suggested to Grothendieck that they should consider a particular prime number. “You mean an actual number?” Grothendieck asked. The other person replied, yes, an actual prime number. Grothendieck suggested, “All right, take 57."posted by Betelgeuse at 12:35 PM on March 18, 2016 [4 favorites]
Source
Jinx, yeolcoatl
posted by Betelgeuse at 12:40 PM on March 18, 2016
posted by Betelgeuse at 12:40 PM on March 18, 2016
I see the Grothendieck prime has been covered already. Me, I got into a groove of automatically pressing N for multiples of 3. That didn't serve me well when 3 itself showed up.
Small-type brag: I scored 68 on a subsequent round
posted by aws17576 at 12:50 PM on March 18, 2016 [1 favorite]
Small-type brag: I scored 68 on a subsequent round
posted by aws17576 at 12:50 PM on March 18, 2016 [1 favorite]
At least 1/3 of my failures are due to me forgetting what 'yes' and 'no' are supposed to be. Answering 'yes' for something that has no factors is really confusing when I'm trying to do it fast.
posted by Betelgeuse at 12:53 PM on March 18, 2016 [2 favorites]
posted by Betelgeuse at 12:53 PM on March 18, 2016 [2 favorites]
I took the test, did OK, read this thread, took the test again and got tripped up by 57 on the first click.
posted by maggiemaggie at 12:56 PM on March 18, 2016 [2 favorites]
posted by maggiemaggie at 12:56 PM on March 18, 2016 [2 favorites]
Curse you 87!!
posted by pattern juggler at 2:37 PM on March 18, 2016 [1 favorite]
posted by pattern juggler at 2:37 PM on March 18, 2016 [1 favorite]
Alternate title: "Do you know your times tables?"
posted by OverlappingElvis at 3:07 PM on March 18, 2016
posted by OverlappingElvis at 3:07 PM on March 18, 2016
Bah. Primes no tingle. Tweet me when you've got a Is this single by a one-hit wonder page.
posted by Twang at 4:16 PM on March 18, 2016
posted by Twang at 4:16 PM on March 18, 2016
Ends in 5? not prime.
digits summed divisible by three? Not prime.
posted by 922257033c4a0f3cecdbd819a46d626999d1af4a at 4:32 PM on March 18, 2016
digits summed divisible by three? Not prime.
posted by 922257033c4a0f3cecdbd819a46d626999d1af4a at 4:32 PM on March 18, 2016
Psst, here's a tip for 57 and 87 (and even 117) if you're kinda good with pattern recognition:
57 + 3 = 60
87 + 3 = 90
117 + 3 = 120
It should be very easy to see that 6, 9 and 12 are divisible by 3, and thus 57, 87 and 117 must be some multiple of 3 and non-prime. (Actually: 60 = 3 x 20, so one 3 less give you 3 x 19 = 57, and so forth.)
posted by tksh at 4:37 PM on March 18, 2016 [2 favorites]
57 + 3 = 60
87 + 3 = 90
117 + 3 = 120
It should be very easy to see that 6, 9 and 12 are divisible by 3, and thus 57, 87 and 117 must be some multiple of 3 and non-prime. (Actually: 60 = 3 x 20, so one 3 less give you 3 x 19 = 57, and so forth.)
posted by tksh at 4:37 PM on March 18, 2016 [2 favorites]
For some reason I couldn't see the entirety of this post so based on the title alone I thought I was going to have to go through a series of products sold on Amazon and determine whether they qualified for Amazon Prime shipping and boy was I mistaken
posted by Hermione Granger at 4:40 PM on March 18, 2016 [2 favorites]
posted by Hermione Granger at 4:40 PM on March 18, 2016 [2 favorites]
I'm the same as Betelgeuse: I'd do much better with "Prime" and "Composite" buttons than "Yes" and "No".
posted by ambrosen at 4:44 PM on March 18, 2016
posted by ambrosen at 4:44 PM on March 18, 2016
If the sum of the digits is divisible by 3, then the number is divisible by 3.
posted by mantecol at 4:53 PM on March 18, 2016 [1 favorite]
posted by mantecol at 4:53 PM on March 18, 2016 [1 favorite]
Am I right in thinking that if the sum of the digits in base n2+1 is divisible by n, the number is divisible by n?
posted by ambrosen at 5:13 PM on March 18, 2016
posted by ambrosen at 5:13 PM on March 18, 2016
Am I right in thinking that if the sum of the digits in base n2+1 is divisible by n, the number is divisible by n?
Or even more generally, any base where base-1 is divisible by n?
E.g. the same rule I stated above works for base 7 (2x3+1). The trick is to make it so that digits carry the same information about their divisibility-by-n, no matter where in the number they are positioned. So "1" means that the value it represents is 1 above being divisible by n, no matter where in the number that 1 is positioned.
I'm not so great with formal mathematical proofs, but it seems to work for all the cases I've checked so far.
posted by mantecol at 6:27 PM on March 18, 2016 [1 favorite]
Or even more generally, any base where base-1 is divisible by n?
E.g. the same rule I stated above works for base 7 (2x3+1). The trick is to make it so that digits carry the same information about their divisibility-by-n, no matter where in the number they are positioned. So "1" means that the value it represents is 1 above being divisible by n, no matter where in the number that 1 is positioned.
I'm not so great with formal mathematical proofs, but it seems to work for all the cases I've checked so far.
posted by mantecol at 6:27 PM on March 18, 2016 [1 favorite]
GOD that stressed me out!
posted by I_Love_Bananas at 6:35 PM on March 18, 2016
posted by I_Love_Bananas at 6:35 PM on March 18, 2016
This brings back horrific memories of primary school. Our teacher had a game where he'd throw the ball to you and you had to catch and say whether that number was prime. If you dropped it, everyone already seated would yell 'fumble!' and you were out of the game and sat down to watch til it ended.
I was shy, uncoordinated but good at maths. Being one of the last three or four kids standing was the worst. Unfortunately, although panic at missing the ball (they were super easy throws) had me frozen with fear it didn't stop me knowing the goddamn answers so I never managed to drop out early and fairly anonymous.
Thirty years on and despite treatment for anxiety that link has made my heart race and my hands clammy. Stupid prime numbers.
posted by kitten magic at 7:02 PM on March 18, 2016 [2 favorites]
I was shy, uncoordinated but good at maths. Being one of the last three or four kids standing was the worst. Unfortunately, although panic at missing the ball (they were super easy throws) had me frozen with fear it didn't stop me knowing the goddamn answers so I never managed to drop out early and fairly anonymous.
Thirty years on and despite treatment for anxiety that link has made my heart race and my hands clammy. Stupid prime numbers.
posted by kitten magic at 7:02 PM on March 18, 2016 [2 favorites]
Up to 37 now! This is the perfect game for someone who spent her time as a kid on long car rides running divisibility tests on all the license plate numbers.
If you need more training ...
posted by sebastienbailard at 10:11 PM on March 18, 2016
If you need more training ...
posted by sebastienbailard at 10:11 PM on March 18, 2016
Wow! I made this. Thank you for rewarding my many many years of lurking with an FPP.
To stoke the competition - the current highest non-tool-assisted score I'm aware of is 73.
> Yes, but is it Numberwang?
An "is it Numberwang?" version is in the works.
posted by warpy at 12:48 AM on March 19, 2016 [10 favorites]
To stoke the competition - the current highest non-tool-assisted score I'm aware of is 73.
> Yes, but is it Numberwang?
An "is it Numberwang?" version is in the works.
posted by warpy at 12:48 AM on March 19, 2016 [10 favorites]
Just got to 53!
posted by peacheater at 6:42 PM on March 19, 2016
posted by peacheater at 6:42 PM on March 19, 2016
I need to learn my 17 and 19 times tables.
More useful: Learn your out chart.
posted by sixpack at 7:47 AM on March 20, 2016
More useful: Learn your out chart.
posted by sixpack at 7:47 AM on March 20, 2016
I clicked on this thread purely to make sure someone had made the Numberwang joke, but I didn't really expect it to be the very first comment. I'm so proud of Metafilter right now.
posted by webmutant at 11:45 AM on March 20, 2016
posted by webmutant at 11:45 AM on March 20, 2016
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posted by Strange Interlude at 11:19 AM on March 18, 2016 [17 favorites]