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Knocking on the wrong door.

June 20, 2008

To all those who landed on this blog via searching for “metric tables”, “ratios,fractions and conversions”, and “metric percentages” , I hope/assume you managed to beat a hasty retreat.All I ever did was bitch about mathematics.I donot recollect teaching maths to anyone.

But as the Lord said -Let Nobody go away empty handed from thy home (Psalm 34.3.4 Book Of David).

So in adherence to the Lord’s sayings here are a few tips (one useless tip rather) for some quick mental math.

A friend of mine (a btech from iit no less) , quite exasperated with my whining, gave me a book which teaches

Trachtenberg’s system of speed maths.

So one thing I learnt there is how to multiply any hugggge number by 12.

************************start of tip****************************

to multiply by 12
Starting from the rightmost digit, double each digit and add the neighbor. (By neighbour we mean the digit on the right.)

This gives one digit of the result. If the answer is greater than 1 digit simply carry over the 1 or 2 to the next operation. Example: 316 × 12 = 3,792:
In this example:

  • the last digit 6 has no neighbor.
  • the 6 is neighbor to the 1.
  • the 1 is neighbor to the 3.
  • the 3 is neighbor to the second prepended zero.
  • the second prepended zero is neighbor to the first.

*************************end of tip****************************************

Heady tips right? Now I just have to find that real life situation where there is a huge crowd and I am being asked to multiply 249894790874 by 12.Hooray!!

But the real ego dampener came when I was showing off my new skills to Sid.He pretended to be impressed with the first one,but inevitably I got the second one wrong and before Icould even put the pen down,he pointed out the mistake.Damn he was doing it in his head and it was a pretty long number I swear.What? Why? When? Is it only me totally lacking in this or there are others ?.Please let me know I have company.

P.S.- Apparently this Trachtenberg chap was a POW during the WW II, and while in the Nazi Concentration camp he came up with this system to -this is the best part– keep himself sane.

Really whatever happened to good ol porn.I pity his cell mate.

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6 Comments leave one →
  1. June 20, 2008 3:16 pm

    Tagged you. Pick it here!

    Hope to see you doing it soon!

  2. June 20, 2008 3:38 pm

    You! That’s right! Just copy paste and start your own bit!

  3. June 20, 2008 3:45 pm

    Got that! Corected it! Just missed that line! Take it forward now!

  4. June 20, 2008 5:00 pm

    Thought about why this would work – and concluded that it would work for 13, 14, 15 etc.. by the same principle. ( except that you have to multiple by 3, 4, 5 etc instead of doubling.. I think it will become more complex once the result of the multiplication becomes > 2 digits, because it has to be accounted for two places to its left..

  5. June 20, 2008 7:07 pm

    If only I had met you back in school … I might have scored hell of a lot better in Math !!!

  6. doodeedoo permalink
    June 26, 2008 10:10 am

    I had to buy the book again 😦 from Landmark ,but it turned out well in the end I bought:

    1) Dave Barry Slept here, 😀
    2) Dilbert Principle (had Dilbert Future)
    3) Tai-Pan- James Clavell.

    hope you are reading it and I will ask what is 736 x 591, when I see you again.

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