# Unexpected answer to sequence riddle

I've got the following sequence:

11+11=4
12+12=6
13+13=8
14+14=?


I've tried multiple approaches:

1. Assuming that the formula is A + B - 18 = C the answer should be 10.
2. Assuming that we write the first number as AB and the second one as CD, and the formula is A+B+C+D, the answer should be again 10.
3. Assuming that we just increment the right part of equation by 2 in each row the answer should again be 10.

But the answer is 1.

Could one explain the rule behind this riddle?

P.S. This is level 55 of this game.

• These kind of puzzles often turn into 'guess what the puzzle creator had in mind'. Above a certain complexity it becomes a subjective choice which explanation is easier or more obvious. For this particular example I think 10 is a much more obvious answer. Given the creator wants the answer 1 one can think of definitions to arrive there. Similarly one could come up with reasonable formulas for a lot of other possible answers. Jul 7, 2023 at 7:59
• @quarague I totally agree. Personally I don't understand why the authors don't show the formula but the plain true/false for an answer. Jul 7, 2023 at 8:19

It looks to me like you have to

sum the digits in each equation until you end up with a single digit:

1 + 1 + 1 + 1 = 4
1 + 2 + 1 + 2 = 6
1 + 3 + 1 + 3 = 8
1 + 4 + 1 + 4 = 10 - but wait! We need to sum the digits again: 1 + 0 = 1

This is technically the same as fljx's answer but feels a bit more puzzly to me.

• Or the answer is just truncated to the first digit. The inputbox had unfortunately a max length of 1 :) Jul 6, 2023 at 20:21
• Thanks for your suggestion, the problem is that the riddle doesn't reveal its logics, it just tells whether the answer is correct or not. Jul 6, 2023 at 20:23

One possible explanation is:

They are all regular sums, but the answers are all mod 9.

11+11 = 22 = 4 mod 9
12+12 = 24 = 6 mod 9
13+13 = 26 = 8 mod 9
14+14 = 28 = 1 mod 9

• Thanks for your suggestion, the problem is that the riddle doesn't reveal its logics, it just tells whether the answer is correct or not. Jul 6, 2023 at 20:24
• pay attention, that 12+12 = 24, not 22 Jul 6, 2023 at 20:25
• The second 22 was a simple typo. The answer is still valid.
– fljx
Jul 6, 2023 at 21:01