Puzzle #2

Puzzle #1 has been solved!  Though I created the puzzle from scratch, a quick web search revealed I wasn’t the first to make a riddle like this.  The solution will be added to the Puzzle #1 page.

Time for a second puzzle.  I’m a little less excited about this one, and a word of warning, this one requires a little bit of knowledge of mathematics to get the answer I want.  But I’m open to hearing what other kinds of answers people come up with, since I’m sure there are other responses that also work.

Without further adieu:

I suspect this is going to be a simple knowledge check, not my greatest of puzzles, but I am curious to see if anyone who knows the answer has trouble answering the question.  As before, a yet to be determined prize awaits the first person to respond to me on this one.  You must respond with the answer I have in mind, or one I like better.

EDIT: I had a few people come to me with answers that are valid, albeit slightly off-base.  To help narrow down the solution, I’m adding one more detail: in this framework, 20 + 8 = 28, but 20 + 8 + 1 = 30.

After a week without a correct response, here is another hint to help solve the question:


The decimal system is a Base-10 number system, using ten numerals, 0,1,2,3,4,5,6,7,8,9. Binary is a Base-2 system, using only two numerals, 0,1. Hexadecimal uses sixteen numerals. If you pick the correct numeric base, you’ll find 8+8 = 17. Which base is it?




The correct answer is Base-9.



    • Not quite what I was looking for, but I realize I’m going to have to sharpen the question a bit. Another common response is to change what the plus operator stands for, which is also a valid answer but not the one I originally had in mind.

      One thing I can add to the puzzle to clarify is this: 20 + 8 = 28, but 20 + 8 + 1 = 30.

  1. Base 9! 8+8 is one full group of 9, leaving a 7 in the one’s place… 17.

    20+8= 28, but 28+1 = 30 because there is no 9 digit in base 9.

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