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Thread: A question about division

  1. #1

    A question about division

    Hello All
    First off I am an adult but never learned basic maths at school so I am learning now via YouTube (and here too I hope)

    I was watching the following video on YouTube https://www.youtube.com/watch?v=_rzq8U78e6M

    The guy that posted this does not seem to be active any more and I have a question which I am hoping someone here can help with.

    Following his example it is quite easy, and I understand it no problem

    then I try the following numbers of my own using his method e.g. 57,197 divided by 19 I start of OK e.g. my first two number are 29 (baring in mind this will end up a 4 digit integer by the end) next I need to deal with the 1 (as in the 1 after the 7 and before the 9) with a remainder of 1 (from 2 into 19 = 9 remainder 1) making 11 and taking the previous number of 9 makes a total of 20 then divide by 2 = 10 so OK,

    so what to do with this 10 (two digits rather than 1) so I carry it to the left and make 29 into 30

    (the final actual answer is 3010 with a remainder, but I will come back to that)

    So I have 30 and the 0 left over from the 10 making 300 (for the first three digits in my number so far) next is I look at 2/9 (the 9 in 57197() I get 4 remainder 1 so my number becomes 3004 at this point ...

    so the point is I have lost track how do I get the 1 in the answer e.g. 3010

    can someone please show me using the method in you tube vido but using my numbers above

    Thanks

  2. #2
    Elite Member mmm4444bot's Avatar
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    The video that you referenced describes an alternate way to divide by 5, 100, or 125.

    You are dividing by 19, so the information in that video does not apply to your exercise.
    "English is the most ambiguous language in the world." ~ Yours Truly, 1969

  3. #3
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    I think you may be referring to the NEXT video, https://www.youtube.com/watch?v=7cBRXayBNr4, which shows two examples of division by 19 using an entirely unrelated "trick" method. (The video you referred to does something I do all the time. This one is completely new to me.)

    The first example is very simple, with no remainders at any step, so it doesn't really show much of the method; the second has remainders, and then runs into a special situation near the end, for which he pulls an additional trick out of his hat. Your example runs into yet another complication. Since he hasn't stated all aspects of the method, but just gave two specific examples, we have no clue as to how he would handle yours!

    I can wave my hands and come up with a way to get the correct answer (which involves doing what he does with the remainder in the second problem, adding 1 to the previous digit of the quotient, and then reworking all the steps so far in order to correct the quotient); but I have no justification for it, and am not sure it is really part of the method. And it's no longer a quick method when you do what I had to do, so what good is it?

    Without any theoretical basis for the method in the first place, there's really not much to say. This is not math, it's magic. No doubt an explanation can be given, but I'd have to work to find it.

    I hope you are aware, though, that this is not how one learns to divide in school; if your goal is just to learn how to divide without a calculator (as opposed to learning quick mental math tricks), then you can totally ignore this. It is not necessary in order to divide numbers.

  4. #4
    Quote Originally Posted by Dr.Peterson View Post
    I think you may be referring to the NEXT video, https://www.youtube.com/watch?v=7cBRXayBNr4, which shows two examples of division by 19 using an entirely unrelated "trick" method. (The video you referred to does something I do all the time. This one is completely new to me.)

    The first example is very simple, with no remainders at any step, so it doesn't really show much of the method; the second has remainders, and then runs into a special situation near the end, for which he pulls an additional trick out of his hat. Your example runs into yet another complication. Since he hasn't stated all aspects of the method, but just gave two specific examples, we have no clue as to how he would handle yours!

    I can wave my hands and come up with a way to get the correct answer (which involves doing what he does with the remainder in the second problem, adding 1 to the previous digit of the quotient, and then reworking all the steps so far in order to correct the quotient); but I have no justification for it, and am not sure it is really part of the method. And it's no longer a quick method when you do what I had to do, so what good is it?

    Without any theoretical basis for the method in the first place, there's really not much to say. This is not math, it's magic. No doubt an explanation can be given, but I'd have to work to find it.

    I hope you are aware, though, that this is not how one learns to divide in school; if your goal is just to learn how to divide without a calculator (as opposed to learning quick mental math tricks), then you can totally ignore this. It is not necessary in order to divide numbers.
    Thanks very much for the advise, I will carry on learning

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