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Faster way to multiply..

Discussion in 'Off Topic' started by Velvathos, Dec 26, 2008.

  1. Velvathos

    Velvathos Lore Keeper
    Stratics Veteran

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    Okay.. So, two random numbers, 41 x 31

    Multiply the first digits of both numbers and you get 12_ now to figure out the next ones..

    Now multiply the last digits from both numbers and get 1 (1x1= 1) and this will be your last digit..

    So now we have 12 _ 1

    Now multiple the the outer numbers and the inner numbers and get 7..

    Answer is 1271

    Let's try that again

    44 x 52

    4 x 5 = 20 and 4 x 2 = 8 and we have

    20_8

    Multiple the outer and inner digits and add them to get 28

    20288 is too big take the 2 and add it to the 20 and get 2288

    The higher digits such as 59x93 we will get into another time.. there is a special trick when you add numbers too big..

    Let's find out what 21432 x 11 is.. Well, do not do the long way with a bunch of steps.. Your first number will be the 2 and then add like this..

    2 + 1 = 3 and 1 + 4 = 5 and 4 + 3 = 7 and 3 + 2 = 5 and the last number will stay so we get

    23575

    Now multiply any digit number that is in the teens such as 16x12.. Add the 2 to the 16 and get 18 And 6 x 2 is 12.. So we carry the 1 to get 192

    You can do it this way with any number in the teens..

    Now what is 54 x 66? Well, let's use this method.. 5x6 = 30 and 4x6 = 24

    30 _ 24

    Multiply the inner and outer digits and add them to get 54.. 305424 is totally not the answer.. add the 5 to the 30 and the 4 to 2 in the 24 and we get 3564 which is the answer.. Let's do that again..

    49 x 87

    4 x 8 = 32 and 9 x 7 = 63

    So are numbers are 32_63

    multiply the inner and outer numbers to get 72 + 28 = 100

    So we have 3210063.. Add 10 in the 100 to 32 and get 42.. And then 0 + 6 = 6 So your answer is 4263

    I didn't get into all the alternative methods.... But, this is an easy way, if you have a pen and paper on you and never have a calculator.. I find these methods easier and I am surprised it is not taught in schools..