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cz
United States3249 Posts
For example: 1, 2, 3, 4, X, what is X? Now that's an easy and obvious one, but the test I'm going to do has some extremely difficult questions. How do I go about studying this? I've tried googling but haven't found an effective method? Any of you math people have a good idea of a way to learn how to identify and do these number series quickly?   | ||
infinitestory
United States4053 Posts
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cz
United States3249 Posts
On October 14 2011 14:20 infinitestory wrote: http://oeis.org/ Can this help me train for a closed-book test? | ||
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infinitestory
United States4053 Posts
if you haven't already, you should learn to derive a polynomial sequence by finite differences | ||
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cz
United States3249 Posts
On October 14 2011 14:24 infinitestory wrote: most likely not; it's very good at finding the formula behind integer sequences, and not much else Yeah, it's definitely a beast for that. I need basically: 1) Some examples of integer sequences from medium to hard 2) How to solve them 3) Their solutions I just need a thought process here. I can almost just go with steps 1 and 3 though, and work it out from there - I assume there a limited number of patterns that you can realistically give for a general public service test, and if I solve 100 or so of them before the test the ones on the best will fit somewhat closely to the ones I practiced. Anyone have a bunch of medium to hard number sequences to solve and break down? | ||
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cz
United States3249 Posts
On October 14 2011 14:24 infinitestory wrote: most likely not; it's very good at finding the formula behind integer sequences, and not much else if you haven't already, you should learn to derive a polynomial sequence by finite differences How do I do that? Also I just need to find the next number in the series, not find an expression that would generate the series. There's also trick stuff like 1,5,2,6,X with X being 3 as it's basically 1,2,X and 5,6,Y basic +1 pattern being interspliced together. | ||
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super_sonic
Singapore5 Posts
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Plexa
Aotearoa39261 Posts
 for instance what level would you consider 1 1 2 6 24 120 X to be?btw these are sequences not series :3 | ||
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whatthefat
United States918 Posts
1) Know your squares and cubes 2) Know the Fibonacci sequence 3) Know the triangular numbers 4) Also be aware of modular arithmetic. The example you gave: There's also trick stuff like 1,5,2,6,X with X being 3 as it's basically 1,2,X and 5,6,Y basic +1 pattern being interspliced together. is actually an arithmetic progression in mod 7 (1, 1+4=5, 5+4=2, 2+4=6, 6+4=3). | ||
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cz
United States3249 Posts
On October 14 2011 14:40 Plexa wrote: Well its hard to know what you define as medium to hard difficulty though for instance what level would you consider 1 1 2 6 24 120 X to be?btw these are sequences not series :3 Medium. Right in the middle. | ||
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Plexa
Aotearoa39261 Posts
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cz
United States3249 Posts
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whatthefat
United States918 Posts
On October 14 2011 14:49 Plexa wrote: Perhaps not! Although it can help with some puzzles, even if it isn't the necessary or intended way to solve the puzzle. I'm not sure what difficulty level this test is at though.Somehow I get the feeling modular arithmetic isn't covered in this! I basically don't have much time to spend on this either. Think 2-4 hours tops. I just need to get through the basic stuff, then I have to move on to studying the logic puzzles and some other basic math. EDIT: In that case, definitely don't worry about modular arithmetic. I would just familiarize yourself with some well known types of number sequences. | ||
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cz
United States3249 Posts
On October 14 2011 14:53 whatthefat wrote: Perhaps not! Although it can help with some puzzles, even if it isn't the necessary or intended way to solve the puzzle. I'm not sure what difficulty level this test is at though. Test spans all difficulties. Starts off really easy then goes up to insanely hard / impossible. I'll find my level of competence / skill, and want to use a few hours of studying to increase that while I can. I'm just not sure how exactly. | ||
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PlutoNZ
New Zealand410 Posts
On October 14 2011 14:40 Plexa wrote: Well its hard to know what you define as medium to hard difficulty though for instance what level would you consider 1 1 2 6 24 120 X to be?btw these are sequences not series :3 The next value is 720. You could read this page: http://www.purplemath.com/modules/nextnumb.htm If you want more help, give me some examples of the problems you will be doing. | ||
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cz
United States3249 Posts
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Jonoman92
United States9103 Posts
On October 14 2011 14:40 whatthefat wrote: I would make sure you know the most commonly used sequences. Specifically: 1) Know your squares and cubes 2) Know the Fibonacci sequence 3) Know the triangular numbers 4) Also be aware of modular arithmetic. The example you gave: is actually an arithmetic progression in mod 7 (1, 1+4=5, 5+4=2, 2+4=6, 6+4=3). Nevermind, just got it upon thinking what the modulus operator did back in Java. | ||
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cz
United States3249 Posts
On October 14 2011 14:54 SearingShadow wrote: The next value is 720. You could read this page: http://www.purplemath.com/modules/nextnumb.htm If you want more help, give me some examples of the problems you will be doing. Thanks!! This is what I was looking for. I'm going to go through it tomorrow and see where I can get. After that I'll have to find some pretty hard sequences and see if I can do them. | ||
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cz
United States3249 Posts
On October 14 2011 15:01 Jonoman92 wrote: Not sure how one would study for this. But the advice already posted sounds decent. Hmm, could you explain that a bit more? I don't really see how from just 1,5,2,6,X it is clear that X=3 is next. Seems like there's insufficient information. Yeah I guess it could be other stuff, but it was just as an example. I could rewrite it to 1,5,2,6,3,X and X = 7. It's just to show that sometimes there are very basic patterns (+1) but they are spliced together with another parallel sequence. There's also stuff like 1/2, 2/4, 3/8, 4/16, where it's adding +1 to the numerator and x2 for the denominator. If you were to rewrite that as a decimal it's hard/impossible to solve. | ||
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Shelke14
Canada6655 Posts
On October 14 2011 14:40 Plexa wrote: Well its hard to know what you define as medium to hard difficulty though for instance what level would you consider 1 1 2 6 24 120 X to be?btw these are sequences not series :3 X= 720? OH shit, I didn't see the guy answered it a few posts above mine sorry! lol | ||
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