But this is obvious?

(741 + 963)/2 = (700+900)/2 + (40+60)/2 + (1+3)/2, it's just average in each decimal place.

Obvious now and really cool in hindsight.

The decimal digits clearly have a conspiracy going on.

That would work in any base, I even think we would find way more interesting coincidences in base 12 (as Sumerians preferred), because it's divisible by 2,3,4,6.

It's unfortunate that we have 5 fingers.

If you count the sections of your four fingers with your thumb, you can count up to 12 on one hand!

If you count with each finger as a binary digit you can count up to 15 on one hand!

255 if you use both hands!

More like 1023 if you also use thumbs but I prefer to use them as carry, overflow bits.

I trained myself to do this by default a very long time ago and I can't imagine counting any other way.

It's so natural, useful and lends well to certain numerical tricks. We should explicitly be teaching binary to children earlier.

I have always counted to 20 on one hand. even as a kid. base, lower joint, upper joint, top. times 5 - including the thumb: my motor memory is trained so that i switch seamlessly from keeping the curse on top of the finger using my thumb, and then, once i cross 16, switch to using the index finger to "cursor" the thumb.

Same here. I have always counted 20 on one hand, so 40 with both. That's how my parents taught me to count when I was little. I used this method so often as a kid that, even though I don't count like this anymore, every number up to 40 still has its own place on my fingers.

It was only as an adult that I realised nobody around me counted this way. You are the first person I have found who talked about this method, so I am glad to find this comment of yours.

I am French and we cont extending our fingers from a closed fist. Typically to 2x5=10.

When I was a kid I relized that I can count the fives on the right hand (1 finger for each 5 on the left), which brought me to 25.

It is only when I was traveling in Asia and watched people on markets that I realized that I can use my thumb to count my 12 other finger phalanges, which brought the total to 144. You just need to know your multiplication table of 12 :)

A system I read about uses the thumb for 5, so that each hand can count (thumb down) 0..4 (thumb up) 5..9.

This gives you the range 0..99. Sweeet.