Search results
Results from the WOW.Com Content Network
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.
Some of the algorithms Trachtenberg developed are ones for general multiplication, division and addition. Also, the Trachtenberg system includes some specialised methods for multiplying small numbers between 5 and 13. The section on addition demonstrates an effective method of checking calculations that can also be applied to multiplication.
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 ...
To multiply a sum (or difference) by a factor, each summand (or minuend and subtrahend) is multiplied by this factor and the resulting products are added (or subtracted). If the operation outside the parentheses (in this case, the multiplication) is commutative, then left-distributivity implies right-distributivity and vice versa, and one talks ...
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.
The Mental Calculation World Cup 2008 was held at the University of Leipzig, Germany on 1 July 2008. It attracted 28 calculators from 12 countries. Adding ten 10-digit numbers, 10 tasks in 10 minutes Winner: Alberto Coto (Spain), 10 correct results in 4:26 minutes. world record; Multiplying two 8-digit numbers, 10 tasks in 15 minutes
Discover the latest breaking news in the U.S. and around the world — politics, weather, entertainment, lifestyle, finance, sports and much more.
With x=2 and y=3 for example, by positioning the top scale to start at the bottom scale's 2, the result of the multiplication 3×2=6 can then be read on the bottom scale under the top scale's 3: While the above example lies within one decade, users must mentally account for additional zeroes when dealing with multiple decades.