Fast Calculus

Hi! I am interested in fast calculus mental and on calculator. I saw that the Chinese have clubs and competitions for mental calculus in China (chinese High schoolers) and the Japanese are more into fast calculus with a calculator. Does anyone here know any books, games, exercises, videos etc to train for both ?? (even in mandarin or japanese languages ; I may use a translation program on the pdfs if needed)

Submitted January 15, 2021 at 01:14PM by JudgmentBusy1571 https://ift.tt/3bHTcn7