5 ms·
Trachtenberg System for Rapid Mental Calculation
- yoz-y 8y agoThe multiplication by 3 seems quite more complicated than just multiplying digits by 3 and carrying over the rest.
- sharemywin 8y agoI always thought this was a neat trick: http://www.archimedes-lab.org/Maths2_Multiplication.html http://www.archimedes-lab.org/Maths2_Multiplication.html
- alfredallan1 8y agoThis seems, at a high level, similar to the various mental arithmetic tricks/pnemonics from India, commonly known as “Vedic Mathematics”. e.g. https://www.quora.com/What-are-some-of-the-best-Vedic-math-tricks https://www.quora.com/What-are-some-of-the-best-Vedic-math-t...
- gshubert17 8y agoI came across this book in the 1960s and remember working through the different algorithms. The only one I remember now is multiplication by 11. More generally, I was not reluctant to do mental arithmetic in school, especially for approximations and sanity checks.