- Pterosaur.net – http://www.pterosaur.net/
2010.01.14
IdeOne
A simple web page that tests code snippets in various programming languages:
http://ideone.com/
Facebook Privacy
Content of this article is replaced by the newer one “Facebook privacy? What Facebook privacy?” at https://eikonal.wordpress.com/2010/04/30/facebook-privacy-what-facebook-privacy/.
Mental calculation of cube root of a six-digit number
Source: posting by Ray Langley to MentalCalculation@yahoogroups.com (Wed, Jan 13, 2010 at 8:27 PM); subject: “[Mental Calculation] Cube Root Extraction Trick”
… Hand a calculator to a friend. Ask him to enter a two-digit number. Have him multiply his chosen number by his number, then multiply it again. Let’s say he chooses number 57. 57 X 57 X 57 = 185, 193 To extract the cube root of this number we must first memorize 1 = 1 2 = 8 3 = 27 4 = 64 5 = 125 6 = 216 7 = 343 8 = 512 9 = 729 Notice that :
To derive the cube root of our number (185, 193), we divide it into two sections at the “comma”.
So, the answer is 57. This feat looks like it requires a great deal of mental ability, but it can be easily learned by anyone in a short time. |
Related:
- cube root calculation – http://xw2k.nist.gov/dads/HTML/cubeRoot.html in NIST’s Dictionary of Algorithms and Data Structures (http://xw2k.nist.gov/dads/)
- Cube Root Calculation System – http://www.mindmagician.org/cubert.aspx at Mind Magician site (http://www.mindmagician.org/)
- How to Do Cube Roots of 9 Digit Numbers in Your Head (1729.com blog) – http://www.1729.com/blog/CubeRoots.html
- How to Do Cube Roots of 9-Digit Numbers – http://www.ehow.com/how_2049759_do-cube-roots-9digit-numbers.html
- Mental calculation (WikiPedia) – http://en.wikipedia.org/wiki/Mental_calculation
Similar here: More simple math wonders – https://eikonal.wordpress.com/2012/03/14/more-simple-math-wonders/ | Mental calculation of cube root of a six-digit number – https://eikonal.wordpress.com/2010/01/14/mental-calculation-of-cube-root-of-a-two-digit-number/ | Squares with just two different decimal digits – https://eikonal.wordpress.com/2010/01/05/squares-with-just-two-different-decimal-digits/ | Number theory finite concidental sums – https://eikonal.wordpress.com/2010/01/05/number-theory-finite-considental-sums/