“Mathematicians call it “the arithmetic of congruences.” You can think of it as clock arithmetic. Temporarily replace the 12 on a clock face with 0. The 12 hours of the clock now read 0, 1, 2, 3, … up to 11. If the time is eight o’clock, and you add 9 hours, what do you get? Well, you get five o’clock. So in this arithmetic, 8 + 9 = 5; or, as mathematicians say, 8 + 9 ≡ 5 (mod 12), pronounced “eight plus nine is congruent to five, modulo twelve.”
Quote by John Derbyshire
Work
Prime Obsession: Bernhard Riemann and the Greatest Unsolved Problem in Mathematics
Prime Obsession explores the historical context, mathematical significance, and personal stories surrounding the Riemann Hypothesis, offering insights into the challenges and mysteries of this enduring mathematical conundrum. more
Author
John Derbyshire
John Derbyshire (born June 3, 1945) is a British-American writer, commentator, and mathematician. He is known for his conservative columns in National Review and his popular mathematics book Prime Obsession. Derbyshire's work spans politics, culture, mathematics, and history, often stirring controversy. Born in England, he later moved to the United States and became a U.S. citizen. His writing style is sharp and challenges mainstream views, especially on race and immigration. more
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