- #1

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## Homework Statement

Fill in the dots:

83 80 84 83 88 95 ...

Pick one of the following answers: 95 91 83 87

## Homework Equations

## The Attempt at a Solution

84-83 = 1

88-84= 4

88 + 7 = 95 ?

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- Thread starter dirk_mec1
- Start date

- #1

- 761

- 13

Fill in the dots:

83 80 84 83 88 95 ...

Pick one of the following answers: 95 91 83 87

84-83 = 1

88-84= 4

88 + 7 = 95 ?

Last edited by a moderator:

- #2

jedishrfu

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What course are you taking?

What book are you using?

What sequences have you learned about?

I don't see an obvious arithmetic pattern to the numbers.

Have you tried to make a case of pros and cons for each of the possible answers?

- #3

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I find it hard to find pro's and cos for each answer. I've learned a large number of sequences yet I cannot figure this one out.

Most other sequences were about linear/multplicative differences (or differences of differences) or using subsequences but they were not hard. This sequence is amidst those so the solution must not be hard to find.

Most other sequences were about linear/multplicative differences (or differences of differences) or using subsequences but they were not hard. This sequence is amidst those so the solution must not be hard to find.

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- #4

jedishrfu

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95 pro its one of the numbers in the list, con there's no case of repeated numbers next to each other in the sequence

91 pro its not in the list, con its -4 from the last number of the sequence

83 ...

87 ...

- #5

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83 ... pro it repeats but other than that there is no good reason to pick it

87 no clue.

87 no clue.

- #6

jedishrfu

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Where did you find this problem?

- #7

berkeman

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Good question. Does not appear to be ASCII or some other similar encoding. I know which answer I would pick, but it still has the con that it doesn't fit any simple pattern, and relies on an assumption about the overall pattern...Where did you find this problem?

- #8

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Please explain as I am clueless.Good question. Does not appear to be ASCII or some other similar encoding. I know which answer I would pick, but it still has the con that it doesn't fit any simple pattern, and relies on an assumption about the overall pattern...

- #9

berkeman

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Explain which part?Please explain as I am clueless.

- #10

jedishrfu

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So if your sequence is from a math book it may be an arithmetic or geometric sequence. If it was from a puzzle book then it might be some more fanciful scheme.

- #11

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What you would pick and why.Explain which part?

- #12

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Like I said it was in a series of other much simpler sequences therefore I would not expect anything out of the ordinary.

So if your sequence is from a math book it may be an arithmetic or geometric sequence. If it was from a puzzle book then it might be some more fanciful scheme.

- #13

berkeman

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Can you tell us where these series were? It would help us to know that.Like I said it was in a series of other much simpler sequences therefore I would not expect anything out of the ordinary.

I'm happy to, but I'd like to see the source first.What you would pick and why.

- #14

jedishrfu

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- #15

Ray Vickson

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Like I said it was in a series of other much simpler sequences therefore I would not expect anything out of the ordinary.

People keep asking you, and for some reason you keep refusing to answer. Is the problem from a book? If so, which book? Is this part of a course, or is it just "recreational math"?

- #16

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People keep asking you, and for some reason you keep refusing to answer. Is the problem from a book? If so, which book? Is this part of a course, or is it just "recreational math"?

Answers:

1) no

2) no

3) Yes, from a basic iq test.

- #17

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A E F

B D G

C

and asks where the H belongs.

- #18

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- #19

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Which two are the most similar of: A cannonball, a pencil, a key? I can loosely defend more than one answer to that ridiculous question and the whole test was somewhat like that. I thought at the time that divining a person's IQ with questions like that was nonsense and I still think so. The question in this thread strikes me as a waste of time for similar reasons.

- #20

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I can see assessment value in something like that is the task is to see how answers you can generate with convincing rationales. That, of course, is not the case here.Which two are the most similar of: A cannonball, a pencil, a key? I can loosely defend more than one answer to that ridiculous question and the whole test was somewhat like that.

The question in this thread strikes me as a waste of time for similar reasons.

I have been following the thread (and working on the puzzle) in hopes that there is a clever, satisfying answer. I would feel

- #21

jedishrfu

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And I underlined the “ger” in one word and “und” in another. Wrong!

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- #23

mathwonk

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lagrange's interpolation formula anyone? (i.e. you can find a (unique) polynomial f(n) of degree ≤ 6 that will give you these 6 numbers for n = 1,...6, and as next number f(7) = any result you want.)

e.g. [(x-1)(x-2)....(x-6)]/[(7-1)(7-2).....(7-6)] equals 1 at x=7 and equals zero at x=1,...6. doing this for each number 1,....7, we can multiply each term by what ever we want, add the results, and get a polynomial that has arbitrary values at x=1,...,7. i.e. just as a linear functionn can pass through any two points with distinct x - coordinates, so also can a 6th degee polynomial pass throug any 7 such points.

So if you are trying to come up with a polynomial rule, this method seems to gives the simplest one possible.

but you can make up any rule you want, like 83 80 84 83 88 95 83 102 112 83 122 135 83 148 164 83......

e.g. [(x-1)(x-2)....(x-6)]/[(7-1)(7-2).....(7-6)] equals 1 at x=7 and equals zero at x=1,...6. doing this for each number 1,....7, we can multiply each term by what ever we want, add the results, and get a polynomial that has arbitrary values at x=1,...,7. i.e. just as a linear functionn can pass through any two points with distinct x - coordinates, so also can a 6th degee polynomial pass throug any 7 such points.

So if you are trying to come up with a polynomial rule, this method seems to gives the simplest one possible.

but you can make up any rule you want, like 83 80 84 83 88 95 83 102 112 83 122 135 83 148 164 83......

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- #24

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Could you please show me your line of reasoning regarding this sequence before we are going too far offtopic?

And I underlined the “ger” in one word and “und” in another. Wrong!

- #25

jedishrfu

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I think we’ve covered everything so far and it’s time to close this thread.

Thanks to everyone for participating.

POST SCRIPT:

Most folks here believe its 83. I hinted at the answer by stopping my pros and cons list at 83 and left it for the OP to come up with pros and cons because ultimately its up to him how he thinks it should be answered. IQ tests are funny tests and it's never clear what the answer is at least to the uninititated.

Sometimes they will come up some really arcane reason that makes sense but its something you wouldn't even think to apply. It reminds me of the Bible Code, a book that was popular a few years ago where people find messages in the Bible by skipping every 10th word, letter or some similar scheme. Basically you can always invent a scheme to match the sequence you have and you can choose any book as the basis for the scheme.

https://en.wikipedia.org/wiki/Bible_code

Another more sophisticated example is the Beale's ciphers:

https://en.wikipedia.org/wiki/Beale_ciphers

which many believe are hoaxes to sell newspapers of the time.

And Veritaseum did a video on a similar sequence asking folks to predict the next number:

Thanks to everyone for participating.

POST SCRIPT:

Most folks here believe its 83. I hinted at the answer by stopping my pros and cons list at 83 and left it for the OP to come up with pros and cons because ultimately its up to him how he thinks it should be answered. IQ tests are funny tests and it's never clear what the answer is at least to the uninititated.

Sometimes they will come up some really arcane reason that makes sense but its something you wouldn't even think to apply. It reminds me of the Bible Code, a book that was popular a few years ago where people find messages in the Bible by skipping every 10th word, letter or some similar scheme. Basically you can always invent a scheme to match the sequence you have and you can choose any book as the basis for the scheme.

https://en.wikipedia.org/wiki/Bible_code

Another more sophisticated example is the Beale's ciphers:

https://en.wikipedia.org/wiki/Beale_ciphers

which many believe are hoaxes to sell newspapers of the time.

And Veritaseum did a video on a similar sequence asking folks to predict the next number:

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