The magic pyramid of numbers
I was blown away when I came across the magic pyramid. I don’t know who discovered it, but here it is –
I simply had to sit and figure out why it worked, and it turned out to rely on the fact that 9 times any of the numbers on the left is almost exactly a string of ones.
Typically, 9 x 123456 = 1111104. If you add 6 (the last digit in 123456), then it does come to a string of ones followed by a 0, that is 1111110
And if you subtract 123456 from that (to get times 8 instead of times 9) you get 1111110 – 123456 = 987654.
Phew! It’s one thing to figure out why it works, but whoever discovered it out in the first place must be somebody with a very special brain.