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The Tabulator: A Machine That Counted Tables Long Before Excel
In the history of computing, a tabulator was a machine that processed statistical data recorded on punched cards.
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Articles, problems and notes on mathematics. Browse by topic or article type.
Problem
The Pythagorean Number Circle: Mysticism and Mathematics
Arrange numbers in a circle, count up and then down, and a square appears. An old puzzle from Yemelyan Ignatiev's book leads to a simple proof.
Problem
Three Brothers and Eight Écus: A Seventeenth-Century French Puzzle
Three brothers take turns giving money to one another and finish with eight écus each. Work backwards or use algebra to discover how much they started with.
Essay
Stepan Yakovlevich Rumovsky (1734–1812)
Euler's pupil Stepan Rumovsky helped shape mathematics, astronomy and education in Russia, from the Academy of Sciences to Kazan University.
Essay
Pythagorean Arithmetic: Perfect Numbers
Why is 6 a perfect number? Explore proper divisors, the Euclid–Euler theorem, Mersenne primes and the enduring mystery of odd perfect numbers.
Problem
Martin Gardner's Matrix Trick
Choose five numbers from a seemingly random grid and their sum is always 57. Try Martin Gardner's mathematical magic trick and discover how it works.
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