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Leo Tolstoy's problem
Leo Tolstoy's problem

Video: Leo Tolstoy's problem

Video: Leo Tolstoy's problem
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The problem has been "walking" on the Internet for a long time, but the controversy does not subside. According to legend, this problem was invented by Leo Tolstoy for the second grade of the parish school. Now only 30% of high school students can correctly solve it, only 20% of university students and only 10% of employees of banks and credit institutions.

Problem 1

The seller sells the hat. It costs 10 rubles. A buyer comes up, measures it and agrees to take it, but he only has a banknote of 25 rubles. The seller sends the boy with these 25 rubles. to the neighbor to exchange. The boy comes running and gives 10 + 10 + 5. The seller gives the hat and change 15 rubles. After some time, a neighbor comes and says that 25 p. fake, demands to give her money. What should I do. The seller goes to the cashier and returns the money to her.

QUESTION

How much the seller was deceived?

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Task 2

"Verbal counting. In the folk school of S. A. Rachinsky "- a picture of the Russian artist N. P. Bogdanov-Belsky (1868-1945), painted in 1895.

The painting depicts a village school at the end of the 19th century during an arithmetic lesson while solving a fraction in the head. The teacher is a real person, Sergei Alexandrovich Rachinsky (1833-1902), botanist and mathematician, professor at Moscow University. In the wake of populism in 1872, Rachinsky returned to his native village of Tatevo, where he created a school with a hostel for peasant children, developed a unique method of teaching oral counting, instilling in village children his skills and foundations of mathematical thinking. Bogdanov-Belsky, himself a former student of Rachinsky, dedicated his work to an episode from the life of a school with a creative atmosphere that prevailed in the classroom.

An example is written on the chalkboard for the students to solve:

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See the comments for the correct answers.

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