Learning shortcuts and simplifiers

[Stryder50]

I'm guessing there may be a few of these to make a thread worthwhile.
I recall seeing this once before and forgot to post it somewhere. Just now saw it and here you go.
The video clip will explain this method. Looks shorter and easier than others, especially if you don't have a calculator (or slide rule like we had when I was in school);

The Japanese Way to Multiply Is So Much Cooler Than Ours​

You have to try it.

The Japanese Way to Multiply Is So Much Cooler Than Ours

You have to try it.

getpocket.com

 

[para bellum]

That is very cool and not something I was taught in school.

I was 12 when Sears came out with their first electronic calculator circa 1972. My dad bought one and we thought it was super cool. I remember it sold for $88.88.

Sears CI 801.58000 Desktop Electronic Calculator

This lightweight desktop electronic calculator has a turquoise and gray plastic case, an array of nine digit keys, and a zero bar and decimal point key below the digit keys. Keys for the arithmetic operations, a percent key, an equals key, and a cancel key are right of these.

americanhistory.si.edu

It wasn't until my sophomore year in HS (1976) when they finally allowed calculators into math class, hand-held calculators were becoming common and I guess they realized they were here to stay.

But I think we lost something in the trade, kids are not taught to solve math problems by hand.

 

[Unkotare]

Not difficult.

 

[luiza]

Slow and long winded .

Take first video example of 21x13 :-
20x13=260
plus
1x13=13

TOTAL 273
Takes about two seconds in your head .
The other way takes an art class plus several days !!!