Mental calculation (2 photos)

"Mental Math. Folk School SA Racha "- a picture of Russian artist NP Bogdanov-Belsky, written in 1895.

The painting shows a village school XIX century during class oral account. The teacher - a real person, Sergey Raczynski.
He was a professor at Moscow University, a botanist and mathematician.
On the wave of populism in 1872 Raczynski returned to his native village of Tatev which created a school with a dormitory for peasant children, has developed a unique method of learning an oral account.
Episodes from the life of the school with the creative atmosphere that reigned in the classroom, devoted his work Bogdanov-Belsky, himself a former student of Racha.





On the blackboard is written the problem to be solved disciples orally in mind:



What is the answer?

No calculators poorly?

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