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The products of small numbers may be calculated by using the squares of integers; for example, to calculate 13 × 17, one can remark 15 is the mean of the two factors, and think of it as (15 − 2) × (15 + 2), i.e. 15 2 − 2 2.
The suanpan (simplified Chinese: 算盘; traditional Chinese: 算盤; pinyin: suànpán), also spelled suan pan or souanpan [1] [2]) is an abacus of Chinese origin, earliest first known written documentation of the Chinese abacus dates to the 2nd century BCE during the Han dynasty, and later, described in a 190 CE book of the Eastern Han ...
Take half of the neighbor, then, if the current digit is odd, add 5. Example: 42×5=210 Half of 2's neighbor, the trailing zero, is 0. Half of 4's neighbor is 1. Half of the leading zero's neighbor is 2. 43×5 = 215 Half of 3's neighbor is 0, plus 5 because 3 is odd, is 5. Half of 4's neighbor is 1. Half of the leading zero's neighbor is 2. 93 ...
Mental calculation is said to improve mental capability, increases speed of response, memory power, and concentration power. Many veteran and prolific abacus users in China, Japan, South Korea, and others who use the abacus daily, naturally tend to not use the abacus any more, but perform calculations by visualizing the abacus.
A mental calculator or human calculator is a person with a prodigious ability in some area of mental calculation (such as adding, subtracting, multiplying or dividing large numbers). In 2005, a group of researchers led by Michael W. O'Boyle, an American psychologist previously working in Australia and now at Texas Tech University , has used MRI ...
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Zerah was reported to have been able to solve fairly complex problems. For example, the sixth Fermat number is 2 2 5 +1 (or 2 32 +1). The question is whether this number, 4,294,967,297, is prime or not. Zerah calculated in his head that it was not and had a divisor of 641. (Its other proper divisor is 6,700,417).
Like Sideways Arithmetic From Wayside School before it, the book resembles more like a puzzle book with a Wayside theme than a novel about Wayside. According to the book's introduction, it was created as a response to Sideways Arithmetic after receiving complaints by students and teachers over the inclusion of the logic puzzles in the story.