5, 11, 17, 23, 29, 41

Please note that I don't have an answer to this problem.

I thought of 2 possible answers,

a) 5 - it is the only single digit number in the sequence.

b) 41 - all other adjacent numbers have a difference of 6

  • $\begingroup$ Did you make this problem up yourself or is it from somewhere else? $\endgroup$ – f'' Aug 28 '15 at 23:18
  • $\begingroup$ I encountered it in an aptitude test. $\endgroup$ – rents Aug 28 '15 at 23:30
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    $\begingroup$ These aptitude tests, are, for lack of a better word, bullshit, because you can answer with any number and defend your answer with a valid argument. I hate 'em. We had an infestation of these styles of puzzles a while back and people started to react negatively to them, but so long as these questions don't get too common you should be fine. Just a heads up, you might get some downvotes from those who hate these "mensa puzzles." (the question is perfectly valid, btw, don't go thinking you have to delete it) $\endgroup$ – Kingrames Aug 28 '15 at 23:44
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    $\begingroup$ @rents I think there is definitely a pattern, see my answer. $\endgroup$ – dramzy Aug 29 '15 at 1:04
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    $\begingroup$ @Kingrames I've noticed that you have a tendency to swear frequently in posts and comments. It's not a super serious thing, and it's not like I'm going to actively enforce it, but would it be possible for you to dial it back a little bit? Thank you! $\endgroup$ – user20 Aug 29 '15 at 3:05

29 is the odd number out because

they're listing every other prime number starting from 5 (prime numbers from 5 to 41 are 5,7,11,13,17,19,23,29,31,37,41) so the sequence should have been 5,11,17,23,31,41 . 29 breaks that sequence.

  • $\begingroup$ This is probably the answer they're looking for IMO. $\endgroup$ – A E Aug 29 '15 at 8:03
  • $\begingroup$ yes, this one is by far the best answer imo. But I think other answers are valid as well. $\endgroup$ – rents Aug 29 '15 at 10:05

5, 11, 17, 23, 29, 41

5 is the answer because

it's the only single digit number.

11 is the answer because

it contains repeating digits, which stands out amongst those numbers.

17 is the answer because

the difference between its digits is the same difference between it and the other numbers around it.

23 is the answer because

its digits are neighbors on the number line.

29 is the answer because

it has the greatest difference between its digits.

41 is the answer because

it is 12 units away from its previous neighbor in the list, rather than 6 like the others (or 5 like the first).

As you can see, each and every answer is the only true answer.

  • $\begingroup$ That is correct, but if you have to choose one which one will you choose (stands out THE MOST), that was what the question was in the test , the questions was single select. I understand your answer though and anyways, this might have been a question just to confuse. $\endgroup$ – rents Aug 28 '15 at 23:53
  • $\begingroup$ Don't consider this a 100% must take serious answer. It's just an illustration of how each and every answer has a valid reason for choosing it. $\endgroup$ – Kingrames Aug 28 '15 at 23:54
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    $\begingroup$ 35 stands out the most because it's missing from the arithmetic sequence! $\endgroup$ – f'' Aug 29 '15 at 0:25
  • $\begingroup$ heh, that works too! $\endgroup$ – Kingrames Aug 29 '15 at 1:00
  • $\begingroup$ Or it is 5 because it is the only number less than 6. $\endgroup$ – Rohcana Aug 29 '15 at 6:52

New answer

When you add up the digits in each number you get:

5, 2, 8, 5, 11, 5

all of these are prime numbers except 8 (1+7), so 17 is standing out the most

Previous answer I agree with b) 41, with a slightly different reason: all numbers are a multiple of 6 followed by minus 1, (5=6-1, 11=12-1, 17=18-1 etc)

Your original answer would never allow the first number to be out of sequence.

  • $\begingroup$ actually 41= 42-1 as well just that we don't have 35 in this sequence. So we are saying the same thing. $\endgroup$ – rents Aug 28 '15 at 23:07
  • $\begingroup$ missed that one, so your reason is better $\endgroup$ – Mousey Aug 28 '15 at 23:11

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