Interesting Math Problem

by 32 replies
33
Here's an interesting math problem being shared on social media...


1 + 4 = 5
2 + 5 = 12
3 + 6 = 21
5 + 8 = ?


The issue I have with this is that I believe there's at least 3 possible correct answers for this...What do you think?
#off topic forum
  • 5+8 = 13 Incorrect answers to other 'problems' don't change that.

    The idea is for someone to become interested in what they think is a bigger pattern and add the number '21' to the answer of '13'?

    So then you would have 3 wrong answers rather than 2?
    • [ 2 ] Thanks
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  • Banned
    The answer is 34.

    (What you're doing is adding the +Numbers to the previous Result Number.) So 2 + 5 [added to 5] = 12.
    • [1] reply
    • That's what I got. But I don't see the other possible answers. Although I completely understand why Kay posted what she did.

      That's such a stunningly obvious answer that I might be convinced that it's right. I was following the pattern rather than the obvious answer. I wonder if it's a male/female thing?
      • [ 1 ] Thanks
  • What are the other two possible answers...besides 34?
    • [1] reply
    • Kay gave one: 13
      J 2.0 gave another: 34

      Another is 43. Take the first number, multiply it with the second, then add the first. This formula works for each of the first three:
      (x*y) + x = n

      There may be other possibilities I haven't thought of...
      • [ 2 ] Thanks
      • [1] reply
  • Yes, that formula works...but that is not the formula used in the OP example.

    The OP example was a straightforward set of additions - there were not further formulaic instructions.

    I'm no math wiz - never was - but I do know the more common way to make a mistake with numbers is to assume something not stated in the formula. I know that because I did it...a lot.

    1 + 4 = 5
    2 + 5 = 7
    3 + 6 = 9
    5 + 8 = 13

    (1+4)+(2+5)+(3+6)+(5+8) = 34
    • [ 3 ] Thanks
    • [3] replies
    • Banned
      Thanks Kay. I see what Kurt means now. There are several solutions.

      : )

    • I tend to agree that 13 is the "most correct" answer. But of course it's not the formula given, as that could be what the exercise is all about, finding the formula from the given info to determine the correct answer. I say not enough info was given, therefore it's best to determine all possibilities and that it's possible that all the equations given are correct if we adjust the formatting a bit of each:


      1 +4 = 5
      2 +5 = 12
      3 +6 = 21
      5 +8 = ?
    • I came up with 37 as an answer.

      1 + (4 x 1) = 5
      2 + (5 x 2) = 12
      3 + (6 x 3) = 21
      5 + (8 x 4) = 37 ***
      • [ 1 ] Thanks
      • [2] replies
  • Kurt -

    I don't necessarily agree with that. You can only do math based on the actual problem presented. Without instructions indicating there is more to the answer - the answer is 13.

    A simple line often included (on intelligence tests) with questions like this is "from the numbers below, extrapolate the most logical answer"....then you would have 34.

    In this case - maybe that is the tricky part? Perhaps the point is to lead people to add their own interpretation to what is a straight forward problem....and arrive at a wrong answer.
    • [2] replies
    • Banned
      Hmm. I disagree with that Kay. There's absolutely nothing to suggest that your way of "solving" the formula is the correct one. (It's just your interpretation of the answer based on the presentation.)

      For instance most people would interpret 1+1=2. However that's just their conditioned response. Depending on the variable it could also mean 1+1=11.
      • [ 1 ] Thanks
    • You don't necessarily agree with me when I said "I tend to agree" with you? Interesting.


      I strongly disagree with your comment:
      In this case there's no reason to assume 34 is any more correct than 43, since they both fit.
      • [ 1 ] Thanks
      • [1] reply
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  • Kurt - This is Sunday. I try not to agree with anyone on Sunday. Have no idea why that is...

    OK - just realized it's still Saturday - been a loooong day - so I agree with you.
  • I see 2 possible answers to the conundrum:

    1) Half past nine;
    2) Quantum physics.
    • [ 3 ] Thanks
  • Applying the pattern to the last equation gives the answer of 96.

    Jason
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  • the difference between the last answer and next answer increases 2 each time
    5*2+2=12
    6*3+3=21=9
    7*4+4=32=11
    8*5+5=45=13
    9*6+6=60=15
    10*7+7=77=17
    11*8+8=96=19

    79*76+76=6080
    80*77+77=6237 =157
    81*78+78=6396=159

    so just say
    1*4+1=5
    2*6=12
    3*7=21
    4*8=32
    5*9=45
    6*10=60
    7*11=77
    8*12=96

    76*80=6080
    77*81=6237
    78*82=6396

    i wonder if mr miller is proud of me finally
    • [1] reply
  • I would say 45.
  • 1 + 4*1 = 5
    2 + 5*2 = 12
    3 + 6*3 = 21
    5 + 8*5 = 45
  • Interesting for who?

    • [ 1 ] Thanks
  • I always end up with 34 lol
    • [1] reply
    • Banned
      (Lol) Maybe the answer to the ultimate question of Life (and The Universe) is 42.

      (Hehe)
      Jonathan
  • 1 ? 4 = 5
    2 ? 5 = 12
    3 ? 6 = 21
    4 ? 7 = 32
    5 ? 8 = 45
  • Since this is presented as a math problem I am with Kay. The answer is 13.

    If the OP presented this as a secret code for messages between two spies I might agree with some of the other answers. Except there is not enough data. Any good spy knows you should always present enough data so the intended reader can only come up with ONE interpretation to your message.
    • [ 1 ] Thanks
    • [1] reply
    • Banned
      I think the beauty of the equation is that it can be interpreted in several different ways. (And, perhaps, why it's been so popular on Social Media.)
  • None of the above. The correct answer is 41. Observe:

    1 + 4 = 5, which expressed in base 6 is also 5.
    2 + 5 = 7, which expressed in base 5 is 12 (1 five and 2 ones).
    3 + 6 = 9, which expressed in base 4 is 21 (2 fours and 1 one).
    5 + 8 = 13, which expressed in base 3 is 41 (4 threes and 1 one).

    • [ 1 ] Thanks
  • 5+8=31

    Calculated according to the above rules
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  • 5 + 8 = 34
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