Fast Addition Trick

How fast can you add four 4-digit numbers? With these magic rods, you can do it instantly!!!

SPOILER:

Pick as many rods as you want, to add the four numbers formed by putting all these rods side by side, you just need to “read” the second line from the bottom (just make sure that you add an additional “2” at the beginning and subtract 2 units from the last digit). 

In the pictures you should read: 29672 and 28763

Can you deduce what's happening? How these rods have been designed?

Apart from a “ready to print” model of 4 rods of height 4, I provide an OpenScad script that can generate as many as 1 540 499 290 different rods of height 4 (= “440 choose 4”) and 34 352 762 009 060 different rods of height 5 (= "5360 choose 4"). You can easily create your own unique set of magic rods!!!

And, by the way, the pointed top allows you to print this model with 0% infill, saving time and material!