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2007
Sat
28
Apr
Miss Loi avatar

A Novel Way Of Doing Your Multiplication

(14)
Tuition given in the topic of Miss Loi the Tutor from the desk of Miss Loi at 1:03 am (Singapore time)

Chanced upon this YouTube video on an interesting way of solving multiplication problems.

Admittedly, this is the first time Miss Loi is seeing this and she thought this might be useful for your anti-careless-mistake-checking procedure in E-Maths Paper 1 (where calculators are taboo).

But then again it’s now well past midnight and Miss Loi is too exhausted after a day of tuition to try this herself. As such she needs a volunteer immediately to try out 1298475326589 X 3055978070712 *types with eyes closed* and see if it works. First one to inform Miss Loi will stand to win a romantic dinner pair of movie tickets … errr … a big and much sought-after and emotional “Well Done & Keep It Up!” message from her.

Hmmm … wonder if they have something similar for division?

Thanks to this blog for the heads up!

頑張って!!!

Revision Exercise

To show that you have understood what Miss Loi just taught you from the centre, you must:

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Comments & Reactions

14 Comments

  1. marina's Avatar
    marina commented in tuition class


    2007
    Apr
    28
    Sat
    5:49am
     
    1

    Wow, thats a really cool method Ms Loi, I enjoyed watching this 🙂

  2. Miss Loi's Avatar
    Miss Loi Friend Miss Loi on Facebook @MissLoi commented in tuition class


    2007
    Apr
    28
    Sat
    8:12am
     
    2

    Good morning marina!

    So you managed to see if this works for 1298475326589 * 3055978070712 already? 🙂

  3. yk's Avatar
    yk commented in tuition class


    2007
    Apr
    29
    Sun
    1:11am
     
    3

    An amazing graphical interpretation of multiplication by breaking the digits up. Once you know why this works, it can be used for polynomial multiplication too!

  4. LB's Avatar
    LB commented in tuition class


    2007
    Apr
    29
    Sun
    1:54pm
     
    4

    So that's mathematicians do, eh? That's pretty amazing, really.. Thanks for the video.

  5. Miss Loi's Avatar
    Miss Loi Friend Miss Loi on Facebook @MissLoi commented in tuition class


    2007
    Apr
    29
    Sun
    8:19pm
  6. nay min thu's Avatar
    nay min thu commented in tuition class


    2007
    Apr
    29
    Sun
    9:47pm
     
    6

    love it.. love it.. love it..

    but mr loi, isn't it a little bit cruel to ask whether it works for 1298475326589 x 3055978070712?

    can imagine counting over 3.968 septillion dots (or 3,968,112,123,416 trillion dots)?? makes me wonder if u regularly torture ur students this way.. haha..

    haha.. anyway, love the video..

    =)

  7. nay min thu's Avatar
    nay min thu commented in tuition class


    2007
    Apr
    29
    Sun
    9:53pm
     
    7

    oops, should be *Ms.. haha.. my mistake.. sorry..

    =)

  8. yk's Avatar
    yk commented in tuition class


    2007
    Apr
    29
    Sun
    11:16pm
     
    8

    haha actually no. My major's in Computer Science, so the maths I deal with is usually discrete.

    On my comment, it could be a quick way to check your polynomial "factorisation" too.

  9. yk's Avatar
    yk commented in tuition class


    2007
    Apr
    29
    Sun
    11:17pm
     
    9

    ok wait on second thoughts, it might be harder to deal with negative coefficients. :S

  10. Miss Loi's Avatar
    Miss Loi Friend Miss Loi on Facebook @MissLoi commented in tuition class


    2007
    Apr
    30
    Mon
    11:53am
     
    10

    nay min thu:

    Yes Mr Loi is a sadistic twisted evil tutor who takes particular glee in traumatizing his students with maths problems such as 1298475326589 x 3055978070712 (without the use of a calculator).

    Miss Loi, on the other hand, is a sweet, gentle and caring tutor who provides Mr Loi with such maths problems 🙂

    Oh well she's babbling nonsense again ...

    Thanks for dropping by!

  11. lostin's Avatar
    lostin commented in tuition class


    2007
    Apr
    30
    Mon
    2:18pm
     
    11

    I also learned a special one during my childhood.

    It can be apply to any 25X25, 35X35 etc. Just add one to the first digit. the final 2 digit is 25.

    E.g. 75X75 is 8X7=56. The answer is 5625. Cheers!

  12. Miss Loi's Avatar
    Miss Loi Friend Miss Loi on Facebook @MissLoi commented in tuition class


    2007
    May
    1
    Tue
    12:58am
     
    12

    lostin,

    How come Miss Loi never learn this in her childhood??? Do you have any more of such tricks up your sleeve?

    Maybe we should consolidate all of our special quirky mathematical tricks in one place and let the students pick the most suitable one depending on the scenario.

  13. mathslover's Avatar
    mathslover commented in tuition class


    2009
    Apr
    11
    Sat
    1:38am
     
    13

    Nice trick! I have one for 11 multiplication also.

    Say we want to multiply the number abcd (NOT a*b*c*d) by 11.

    Ones place: d
    Tens place: c+d (if >10, keep the ones place and carry 1)
    Hundreds place: b+c (+1, if the tens place got carry one, and again if total >10, keep the ones and carry 1)
    Thousands place: a+b (+1, if the hundreds place got carry one, and again if total >10, keep the ones and carry 1)
    Ten-thousands place: a (+1, if the thousands place got carry one)

    Example: 2392 x 11

    Ones place: 2
    Tens place: 9+1=11, so tens place is [1] and carry 1
    Hundreds place: 3+9+1 (cos just now carry 1) =13, so hundreds place is [3] and carry 1.
    Thousands place: 2+3+1 (cos just now carry 1) =6
    Ten thousands place: 2

    Answer: 26312

  14. confused's Avatar
    confused commented in tuition class


    2012
    Feb
    6
    Mon
    1:08am
     
    14

    hey it was really nice trick ms. loi
    but, how can i solve e.g 69*89?

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