Have you ever heard of people using their hands to multiply two numbers?

Yes. A student showed me that once.

I do that all the time. My public school teachers weren’t that good so we had to figure out stuff like this on our own. Ot works fine and is rather accurate.

I’ve seen people use some hand system, to the nine part of the multiplication table. I never used it…

Never heard this. Was never taught in my daughters years of schooling either. Tricks for this are useless in my opinion.

I sometimes do this.

I never heard of this. I only have 10 fingers counting my thumbs so seems a little worthless to me. 2×6 and I’m already lost!

You count by 6 – 6 then 12 and raise a finger each time. When you get to 2 raised fingers you are done, so 2×6=12

I suspect this idea has been around for a long time. Our decimal number system is a reflection of our 10 fingers. The word digit, in addition to its numerical meaning, can also be a finger.

In another Q I mentioned we learned about mathematical base systems. Base 2, base 7, Base 10, etc.
As and exercise we learned to count with our fingers in base 2 and base 6.
In base 2 you can count to 1023 with 10 fingers. That worked but got confusing.
Counting to 35 was easy if we used base 6. Fist is zero, right hand is units, and left is powers of 6. It was easy to keep on track.

How did you count in base 2? Did you have each finger represent 0 or 1 in a 10 digit number and then keep adding 1 base 2? I can see that as being a little tough. Working with base 6 up to 35 shouldn’t be too bad. That was a good teaching method for learning about other bases.

Do you think this was something that should have been taught in school @Acrylic? Seems like a fun waste of time to me. Time better spent teaching cursive. ;)

@Dutchess_III It worked for me, was the only way to get a passing grade. They taught cursive, tried anyway, but I prefer to print. Public schools here are a joke. New high school opened recently, and they were all bragging that 5 of their students got accepted to a local community college whose standard in a 2.0 gpa. Good for those students, sure, but not good to brag on that’s the best you can expect.

Yes.

One Korean technique called chisanbop teaches primary grade students a technique using all 10 fingers on both hands -

https://m.facebook.com/Drive.To.Share.Science/videos/using-fingers-to-calculate/299220414662109/

It’s fast and accurate, but was largely rejected in the US after 1985 because it only emphasized calculation.

Many students who learned the chisanbop/abacus method were found to lack understanding of the basic number facts needed for more advance math like algebra & calculus.

Another, quite old hand counting method, is base 12. Counting the knuckles on each four fingers.
It is speculated that this system gave rise to, or coincided with other important factors in history, and measurement. 12 months in a year, made of 24 hour days etc. 12 inches in a foot. 12 apostles, 12 doorways on certain Islamic structures, etc. There are many examples…

@LostInParadise To count on your fingers in base 2 open your hands wide. Each finger is a power of two. Curl the finger to make zero. Extend the finger to make 1. But never, ever ask the class to represent 4 or 128, or worse, 132!