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Since 9 = 10 − 1, to multiply a number by nine, multiply it by 10 and then subtract the original number from the result. For example, 9 × 27 = 270 − 27 = 243. This method can be adjusted to multiply by eight instead of nine, by doubling the number being subtracted; 8 × 27 = 270 − (2×27) = 270 − 54 = 216.
The iPhone calculator is great for crunching numbers in a pinch, but you can also use it to have some fun with your friends and family. Here are some cool calculator tricks you can use to find ...
Trachtenberg system. The Trachtenberg system is a system of rapid mental calculation. The system consists of a number of readily memorized operations that allow one to perform arithmetic computations very quickly. It was developed by the Russian engineer Jakow Trachtenberg in order to keep his mind occupied while being in a Nazi concentration ...
Mathematical joke. A mathematical joke is a form of humor which relies on aspects of mathematics or a stereotype of mathematicians. The humor may come from a pun, or from a double meaning of a mathematical term, or from a lay person's misunderstanding of a mathematical concept. Mathematician and author John Allen Paulos in his book Mathematics ...
It was fun to try to peck out words. 53045 looked like “shoes.” 5508 resembled “boss.” 37818 was “Bible” and 7734 was “hell.” This eventually led to the forbidden number 5318008.
261. ISBN. 0-8050-6299-8. The Number Devil: A Mathematical Adventure ( German: Der Zahlenteufel. Ein Kopfkissenbuch für alle, die Angst vor der Mathematik haben) is a book for children and young adults that explores mathematics. It was originally written in 1997 in German by Hans Magnus Enzensberger and illustrated by Rotraut Susanne Berner.
Little Professor with accompanying booklet. The Little Professor is a backwards-functioning calculator designed for children ages 5 to 9. Instead of providing the answer to a mathematical expression entered by the user, it generates unsolved expressions and prompts the user for the answer. [ 1]
Author of many popular science and mathematics books, including Mathematics Can Be Fun. D. R. Kaprekar: Kaprekar: 1905: 1986: Indian Discovered several results in number theory, described several classes of natural numbers including the Kaprekar, harshad and self numbers, and discovered the Kaprekar's constant: Martin Gardner: Gardner: 1914: ...