# How can 15 become 3?

This is not a mathematical puzzle.

How can 14 become 7?
10 becomes 1, but can also become 2.
13 becomes 8, and 8 becomes 10.
6 stays as 6 under this thinking.

Credit to the series Deltora Quest for this riddle concept. I merely changed one thing about it, and used different numbers. If any of you have read it, you'll get why this is in spoiler tags!

Hint 1:

Don't think of the second in the pair as numbers... perhaps having them in tally form may help you? Some more pairs: 15 becomes 4, as well as 3. 10 can also be 5 or 9, along with 1 or 2 (maybe I should say... "one" or "two"?).

Since answer was found, OP note:

The original puzzle used 11 and 9, and e's were written as "E". As mentioned above, I changed the "E" to a pitchfork shape, eliminating one tally.

• Not a mathematical puzzle, still the use of no-computers.
– m4n0
Commented Jul 26, 2018 at 9:41
• Yes! The puzzle does not require mathematical knowledge, and you could find out what the puzzle was quite easily if you looked up my credits spoiler. Additionally, the solution to this puzzle is best drawn on paper- Commented Jul 26, 2018 at 13:43

This is because

the first number is the number of sticks required to create the second number in words, ie. it takes fifteen sticks to make the word three.

• There it is! Yes, and the same... "font", so to say, can be applied to the rest of the numbers as well. Commented Jul 26, 2018 at 14:05
• Thanks! I loved the rot13(Qrygben Dhrfg) series, I'm so glad to see it's still got some readership! Commented Jul 26, 2018 at 14:09

That's because:

14 = 6 + 8
6 stays as is
8 becomes 10
10 becomes 1
6 + 1 = 7

15 = 13 + 2
13 becomes 8
8 becomes 10
10 becomes 1
1 + 2 = 3

• Please use spoilers. Commented Jul 26, 2018 at 5:07
• Thanks for giving the puzzle some thought! Alas, this puzzle has nothing to do with math of any kind. Since the puzzle is over 12 hours old, I'm adding the first hint :) Commented Jul 26, 2018 at 13:40
• "...math of any kind" or replacement of numbers, I should say. But you are definitely close with the thinking that numbers are getting "moved around" in some way, though with themselves. Commented Jul 26, 2018 at 13:47

My try:

(Note that I know nothing about the Deltora Quest, and the rule may be too far-fetched for the given numbers.) The rule is: If your number is too large*, divide it by five if you can**, or divide by two if you can, otherwise spell your number out in words and take the letter count. If your number is small, spell out your number twice and take the letter count again.
So, 15 -> 3 (divisible by 5, so 15/5=3), 14 -> 7 (divisible by 2, so 14/2=7), 10 -> 1 or 2 (10/5=2 or (10/5)/2=1, depends on the 'or' interpretation as exclusive or not), 13 -> 8 (13 is not divisible by 2 or 5, so 13 (thirteen) -> 8 letters), 8 -> 10 (8 (eight) -> 5 letters -> 5*2=10), 6 -> 6 (6 (six) -> 3 letters -> 3*2=6).
Note that dealing with letters count makes (in my opinion) the puzzle non-mathematical, since it depends at least on the language the puzzle is written in.
* "small" numbers mean one-digit ones, "large" all others.
** "if you can" means if the result is an integer.

• You are close with the "otherwise..." idea! That is the right track. You also bring up a good point about language; I will add that tag. Commented Jul 26, 2018 at 13:38