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Learning via games - prime factorization

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
Expert replies
by saritalr » Mon Aug 02, 2010 12:14 pm
All my test prep resources keep emphasizing how important it is to know the prime numbers and prime factors for test day. I've been trying to find some fun/easy ways to memorize the prime numbers, but haven't had much luck. While I do know how to figure out the primes, I'd prefer to just know them.

Finally, I gave up trying to find a memorization trick. I broke the primes down by groups of 5 and practiced while running on the treadmill. Now I feel pretty confident about the primes up through 71. But if I'm honest with myself, I know that unless I find some way to think about them on a daily basis, that memorization will go up in smoke in a few short days (maybe hours?).

Enter Prime Shooter. I've played for about an hour this afternoon, and it's great. Clearly, its entertainment value is somewhat limited, but it's better than falling asleep over flash cards. Hopefully others on the forum will find it helpful as well.

If anyone has another game or a memory trick, please feel free to share. Maybe even a song?

Thanks in advance.
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Source: — Quantitative Reasoning |

by KrazyKarl » Tue Aug 03, 2010 8:53 pm
I had a teacher tell me one time that prime numbers have to be next to multiples of 6 so maybe that helps to memorize them:

2 and 3 are your first 6, but then:

5 and 7 are next to 6

11 and 13 are next to 12

17 and 19 are next to 18

23 is next to 24

29 and 31 are next to 30

37 is next to 36

41 and 43 are next to 42

47 is next to 48

53 is next to 54

59 and 61 are next to 60

67 is next to 66

71 and 73 are next to 72

It might not be that helpful but if you think in multiples of 6 for some reason it could make it easier or at least be a quick way to check them.
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by shashank.ism » Tue Aug 03, 2010 10:09 pm
krazykarl, you teacher has given a very good way to memorize this & this 6 thing is really interesting, I never noticed it or read it somewhere..
Your teacher might have figured out this...and this one is really helpful for many people here.....thanks anyway... :)
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