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Just multiplied a 10 digit number by 12 in my head!! Blog Discussion

This is a chat forum discussion on Martin's 'Just multiplied a 10 digit number by 12 in my head!!!!!' blog which you can read here.
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  • quoiaquoia Forumite
    14.4K Posts
    Part of the Furniture 10,000 Posts Name Dropper Photogenic
    He's obviously had a bout of MENTAL Arithmatic..
    There are 10 types of people in the world. ‹(•¿•)›
    ‹(•¿•)› Those that understand binary and those that do not!

    Veni, Vidi, VISA ! ................. I came, I saw, I PURCHASED
    S LOWER CASE OMEGA;6.59 so far ..
  • nelly_2nelly_2
    17.9K Posts
    10,000 Posts Combo Breaker
    I got one of them memory books once and its sort of usefull I managed to memorise the serie A in order for that particular week and you can apply it to anything, but and as daft as it sounds you dont remember to do it when you put the car keys down and thats why you cant remember where they are.

    This numbers one sounds more usefull though I hardly ever have to work things out anyway.
  • TicklemouseTicklemouse Forumite
    5K Posts
    Hell - I still have to think about 8 x 7!! :rotfl:
  • bigandy_3bigandy_3 Forumite
    42 Posts
    I was intrigued by the ability to learn a new skill and party trick (imagine: "I bet you £20 I can multiply a ten digit number by 12 in my head!"), so I found the following page which gives you an idea of the technique;


    But my word! It's not exactly straightforward !
    if i had known then what i know now
  • MSE_MartinMSE_Martin MoneySaving Expert
    8.3K Posts
    Dont worry the book includes exercises and makes it much easier to do. And let me clarify what 'multiply a 10 figure number by 12 in my head' means.

    While i can (sometimes) do three figures by two figures now ie 248 x 38.

    As for the rocess of a 10 figure by 12 in my head, you effectively do it one digit at a time (in reverse!) i couldn't remember it.

    Thus if someone said multiply 2285643939 by 12, I couldn't reel off the number. However I could write it down without any workings :)

    Martin Lewis, Money Saving Expert.
    Please note, answers don't constitute financial advice, it is based on generalised journalistic research. Always ensure any decision is made with regards to your own individual circumstance.
    Don't miss out on urgent MoneySaving, get my weekly e-mail at www.moneysavingexpert.com/tips.
    Debt-Free Wannabee Official Nerd Club: (Honorary) Members number 000
  • CISCIS Forumite
    12.3K Posts
    Part of the Furniture 10,000 Posts Name Dropper
    Theres a good intro to the system here

    I no longer work in Council Tax Recovery but instead work as a specialist Council Tax paralegal assisting landlords and Council Tax payers with council tax disputes and valuation tribunals. My views are my own reading of the law and you should always check with the local authority in question.
  • dchurch24dchurch24 Forumite
    1.2K Posts
    Part of the Furniture 1,000 Posts Combo Breaker
    That's bizzarre! My dad had this book on his bookshelf when I was roughly 16 (he'd bought it a train station while waiting for a train one day many years ago), and I'd found it and read a little bit of it and found it quite interesting.

    A few years later (about 15 years actually), I was telling a friend about it and I couldn't find the book anywhere, so we both bought a copy on Amazon and amazed each other with ridiculous sums over the phone.

    Indeed, this method of maths is the ONLY method they teach in Switzerland - my partners family all live in Switzerland and so I asked them to verfy the claim in the book and it's true - apparently!

    Very good read - even the intro which is a brief history of Tractenburgs life.
  • En_KayEn_Kay Forumite
    1 Post
    You should try Rapid Math Tricks and Tips by Edward Julius. It contains various tricks to enable mental multiplication/division etc.. Some are very, very simple.
  • sneekymumsneekymum Forumite
    4.8K Posts
    Read the reviews of this similar (but clearly inferior) book...

    (start at the bottom)
    still raining
This discussion has been closed.
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