Can you name the twin primes between 1 and 100?

created by ysumath

Enter a number pair in the box below
Correctly named number pairs will show up below
Answers do not have to be guessed in order
Twin primes are pairs of primes which differ by two. Enter the pair separated by a space or comma in numerical order.
Also try: Two Minute Math: LCM

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Twin Primes

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Twin Primes

Twin Primes

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There are 26 comments for this game.
(Warning: comments may contain spoilers)

Twin Primes Quiz

by ysumath

Created Apr 18, 2011 in Science
Featured Apr 28, 2011
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Archived comments: show them

	rockgolf:	Apr 28th, 2011 at 17:07 GMT		28 points
	Does that make 2 & 3 Siamese twin primes?

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	shawnoc:	Apr 28th, 2011 at 18:07 GMT		20 points
	That would take so much more time.

	ostroffj:	Apr 28th, 2011 at 18:21 GMT		6 points
	@shawnoc: It would take strictly less time than forcing someone who writes out "five, seven" to delete it and write "5, 7" in its place. I think it's good to accept wordier forms of answers and then have the abbreviated form pop up instead, as a way of telling the solver that there's a better way to do things without punishing them for starting with the formal route.

	puckett86:	Apr 28th, 2011 at 18:25 GMT		51 points
	@rockgolf Good one, but rockgolf already made that joke in the archived comments.

	mcdonald123:	Apr 28th, 2011 at 23:26 GMT		-1 points
	I was sure 27 and 29 was one. I always have struggled with 3x9...

	rockgolf:	Apr 29th, 2011 at 00:21 GMT		14 points
	@puckett86: Dammit! He steals all my best material.

	rockgolf:	Apr 29th, 2011 at 00:27 GMT		3 points
	@mcdonald123: Here's the easy way to remember the 9x table. Hold your hands in front of you, with all your fingers sticking out as if you were blocking something from hitting your face. Now bring down your left baby finger. You've got zero fingers to the left of the baby finger, 9 to the right. 1x9=09. Put your baby finger back up and bring down your left ring finger. The remaining fingers represent 1 & 8. 2x9=18. With the left middle finger, 3x9=27. Moving each finger down one at a time gives you the 9x table.

	lizzyloo:	Apr 29th, 2011 at 00:58 GMT		3 points
	took me a few seconds to figure out the directions, but I somehow got them all with 5 seconds to spare! yay!

	gvigary:	Apr 29th, 2011 at 14:20 GMT		1 point
	Can't believe I missed the second pair because I didn't think about re-using one :facepalm:

	CaptHayfever:	May 1st, 2011 at 06:17 GMT		4 points
	@lizzyloo: That's why I try to figure out the directions before I start the clock.

	climber_v12:	May 2nd, 2011 at 13:38 GMT		-1 points
	I would make the suggestion that phrases such as '5 and 7' should be accepted. I know it might have been difficult to think of all of them at the time of making this quiz, but perhaps the suggestions could now be taken to make it better.

	climber_v12:	May 2nd, 2011 at 13:39 GMT		-2 points
	And before someone says it is faster to type '3 5', some people (including myself) can type 'and' in less time than it takes to say it.

	ysumath:	May 3rd, 2011 at 01:18 GMT		1 point
	I can't edit it anymore. Sorry.

	Cecispanda:	Dec 30th, 2011 at 22:53 GMT		3 points
	I know this has been up for a long time -- but I have a question that probably shows my ignorance. Why do 1 and 3 not count? Is 1 simply not defined as a prime? I thought a prime was defined as a number that had no factors other than 1 and itself, which 1 would meet.

	SteelyMatt:	Jan 8th, 2012 at 04:06 GMT		3 points
	@Cecispanda: The reason that 1 is not considered a prime number is because a prime has to have at least two DIFFERENT factors. Being divisible by "1 and itself" implies that 1 and "itself" are distinct numbers.

	merxes:	Apr 28th, 2012 at 20:39 GMT		0 points
	not enough time

	mrdannydoodah:	Dec 6th, 2012 at 01:46 GMT		2 points
	@SteelyMatt you mean EXACTLY two different factors, where 1 is counted as a factor, not AT LEAST two, eg 12 has at least two factors (1,2,3,4,6) but is not prime even though your definition would suggest it is.