# What's wrong with this D20?

Here's a D20 I produced by 3D printing and finishing. Something is wrong with it relative to the intended design. What is wrong and how did it get to be that way?

Hint:

For the second part of the question, fill out as much of the net as you can from the visible faces and compare it against a plausible intended net. Can you extend the partial net to a full one where there's an explainable pattern to the discrepancies?

• I assume you wanted it to be organized in opposite numbers to have the sum 21. Right?
– Moti
Aug 28 '19 at 2:02
• @Moti: Figuring out the intent is part of the puzzle. :-) Thus the tagging. This is my first question post on this SE site so I hope I'm doing it right. Aug 28 '19 at 2:04

It's conventional for dice to have opposite faces sum to $$n+1$$, but on the die pictured, 6 is adjacent to its compliment, 15.

• This is correct, and answers the first part, but can you figure out how it got that way? Aug 28 '19 at 2:42

For the second part:

The only way I can see this happening is if the net you used for the numbers has at least two essentially different methods of folding, but which net did you use...? Or, when the net was being made, someone put the numbers in the wrong places.

My guess is:

The die maker got confused between the 6 and the 9 - so opposite the 6 is 12, and opposite the 15 is 9.

What is wrong

to me it looks like 18 appears twice, if the number between 5 and 6 is a 15, then

how did it get to be that way

the 6 could be a 9 because of some mirroring but I am not sure if the line is a scratch or not

What is wrong in the image:

15 is next to 6, violating the usual dice rule of the sum of complements being equal unless 15 and 6 are duplicated

Observations:

Filling out a d20 net with the visible values and assuming that adding complements yields 21, all values except 8,9,10,11,12,13 are present, with 6 and 15 doubled. There are 4 unknown spaces which I assume contain 7,14 and 5,16

why?

Trying to avoid middle values in tabletop gaming?