@[email protected]M to [email protected] • 11 months agoMental Calculation. In Public School of S. A. Rachinsky - Nikolay Bogdanov-Belsky (1895)upload.wikimedia.orgimagemessage-square3fedilinkarrow-up177arrow-down11
arrow-up176arrow-down1imageMental Calculation. In Public School of S. A. Rachinsky - Nikolay Bogdanov-Belsky (1895)upload.wikimedia.org@[email protected]M to [email protected] • 11 months agomessage-square3fedilink
Never seen this before. It’s incredible!