April’s Newsletter Riddle – Answer

The Riddle:

In Germany there are calendars made of wooden blocks for very bright kids.  There are two six sided dice, and by choosing which face is displayed for the two of these, all possible monthly dates (from 01, 02, …, to 29, 30, 31) can be displayed; note the single digit dates must start with a 0.

Your job is to write one digit (from 0, 1, 2, …, 8, 9) on each face of the two dice so that this can be done. Good luck!

The Solution:

So, I figured I should have some idea of how to work out this riddle before the answers, or questions, came pouring in. I thought about the riddle some, and decided the easiest way to solve it would be to actually physically see the two cubes.

I “googled” (as you do when you start out on a new project) and came across a cube net. I saved the net, and printed out two copies of it – for the two cubes.

And then I had a revelation. There are ten numbers that need to go on the cubes and 12 spaces – 2 of the numbers had to be repeated… But which two?

My first theory was that 1 and 2 should be the repeated numbers, so I wrote 0, 1, 2 and 7, 8, 9 on one cube and 1, 2, 3, 4, 5, 6 on the other cube and began testing my theory by going through each individual date. 01 to 06 worked perfectly but then I hit a snag… my 0 was on the same die as my 7… oh no!

Back to square one (pardon the pun) – erase all the numbers and start again….

Thankfully I had stuck my cubes together with prestik.

I thought about it a bit more. And then did some more thinking. No brilliant ideas popped into my head. The biggest problem seemed to be that we need a repeat of 0, 1 and 2 – which is one repeat too many. Uh oh!

I remember seeing a set of these dice on my sister-in-law’s windowsill. I wish I had paid more attention to them.

And then after much stalling, I had a eureka moment! I realized that you can turn the 6 upside down to make a 9! Felt like a genius! Wanted to dance around the office – but that might have been a bit inappropriate sadly. But you know the feeling when everything suddenly clicks into place.

So now I can have 0, 1, and 2 on both die because I only have 9 numbers to write instead of 10!

So on my my first die, I now have 0, 1, 2, 5, 7, 8 and on the second die I have 0, 1, 2, 3, 4, and 6 (slash 9). Tada!!

All that without a cup of coffee – Oh yeah!