I'm trying to solve a number sequence question that goes like this:

15, 14, 30, ?

This question gave four options, 29, 28, 27, and 26.

I think that 29 and 28 are both correct but this only accepts one answer.

29 is correct since 15 -1 = 14, then 14 + (15+1) = 30, so its plus then minus, so 30-1=29 Using this sequence, we can tell that the next number after 29 would be 29+(30+1)=60.

28 is also correct since this looks like a multiplication puzzle, since the first number is 15 and the third number is 30, which is 15x2. So, the number represented by the question mark, which is the forth number, would be 14x2=28. The next number after 28 would be 30x2=60.

I have a feeling that 29 is a better answer than 28 as I found many more evidences that leads to the number 29. However, I also feel that 28 is also correct. However, as I've said, you can only choose one answer. So which is the best answer?

  • 3
    $\begingroup$ This seems to be very opinative. It could be whichever number you want it to. Example: i.imgur.com/sQSFMPb.jpg $\endgroup$ Oct 29 '20 at 1:39
  • 6
    $\begingroup$ If you are taking an exam somewhere and you have been presented a question like this, and there is no other tip or clue somewhere else, I would really think that the exam is worthless and would complain about this wherever or to whoever I could to. $\endgroup$ Oct 29 '20 at 1:42

That question suffers from exactly the problem described here:

All of the [reasons why such puzzle is bad] mean that any such question reduces to a guessing game where the asker continually rejects apparently valid but not intended solutions, which is a sign of a poor puzzle.

For the specific question, even if we exclude arbitrarily constructed rules, 29 and 28 are equally valid because both can be explained with simple rules.

There is no best answer you can figure out just by looking at the question and choices. It is a guessing game between you and whoever made up this question. Surrender and throw it away immediately.

  • $\begingroup$ Yes, I agree. While I was attempting this puzzle, I found this very vague and wondered why would such a vague puzzle even exist. If it allowed us to choose more than one answer, then its way better since if we made the wrong choice which is correct, we would lose marks for nothing. $\endgroup$
    – Pilot
    Oct 29 '20 at 1:51

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