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Homework Help: Physics Lab - greatest common factor between all these numbers

  1. May 12, 2014 #1
    Physics Lab -- greatest common factor between all these numbers

    1. The problem statement, all variables and given/known data
    Hey, how can I find the greatest common factor between all these numbers? Please reply as soon as possible, it is an assignment due tomorrow.

    2. Relevant equations
    No equations used.

    3. The attempt at a solution
    My attempt was that I entered all these value on excel, I converted all these numbers to whole numbers. I used =gcf on a cell, and in brackets I put all that data. It gives me a common factor of 1, apparently that answer is wrong, my teacher even said. I need the common factor in decimal form. I even converted it back to decimal form, which is 0.01, and that answer is also wrong. Gow can I get the common factor in decimal form?
    Last edited by a moderator: May 13, 2014
  2. jcsd
  3. May 12, 2014 #2


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    I have no idea what you are wanting to do. Do you think there may be a decimal fraction, something like, say, 0.21045, by which you can neatly divide each of your data values? I doubt it.

    Perhaps you could explain what data you are trying to process this way?
  4. May 13, 2014 #3

    Hey, the purpose of this is to find a mass of one gummy bear and to simulate milikan's experiment. What we did first is found the mass of 15 gummy bears, then I rearranged form lowest mass to highest. Then I found the first differences between the gummy bear bags. I averaged the ones that were around 2, 0, and 1. I did it because there would be less numbers to common factor. The highest common factor between all the differences is the mass of one gummy bear. And I got excel to do it and it gives me one. I know that is wrong because other people in my glass got around 2.5 grams, the teacher said it is around that much. I have a excel file attached, open it to see what I did. What I am trying to figure out is a greatest common factor, can you show me how to do it without technology, like just give any example and show it. Also the gcf has to be a decimal number. Please reply as soon as possible, I have to hand it in tomorrow.

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  5. May 13, 2014 #4


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    Try it without the average. When you average you're going to change you're GCF:
    look at something like 3 and 12 where 3 is the GCF, average them it's 15/2, well, then I take a 3 and 9 GCF is 3, but averaging gives 6, and what's the GCF of 15/2 and 6? it's not 3, that's for sure. (extreme example)
  6. May 13, 2014 #5
    The purpose of why I averaged some is because then there would be less numbers to common factor. For example, 2.01,2.015,2.25,5,10,13,15. I would take the avg of 2.01, 2.015,2.25. Which is 2.06. Then the set I have to common factor is then 2.06,5,10,13,15. The problem is that I am trying to figure out how to common factor decimals. The example I just gave in this reply is made up, not the numbers I got in the lab. I just made it so you get my point.
  7. May 13, 2014 #6


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    This still doesn't make a lot of sense.

    If you weighed 15 gummy bears, then you should have a good idea regarding the reprexentative weight of a gummy bear.

    Looking at your spreadsheet, it seems that you weighed 15 different bags, each containing an unknown number of gummies. Right?

    Another mystery regarding your data:
    For bags numbered 6,7,8: Each has two masses listed. Each pair being way different from each other.

    For the bag numbered 9: You have 4 different masses. They jump all over the place.

    You really need to describe much more thoroughly, precisely what the numbers all represent.

    BTW: There's no need to subtract out the empty bag weight, if you do first differences.
  8. May 13, 2014 #7
    For the ones it looks like they have 2 masses because I forgot to delete some rows. I will do it and resend it.
  9. May 13, 2014 #8
    Fixed copy of excel document

    Yeah each has an unknown number of gummy bears. Also the averaged ones are on sheet 2.

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  10. May 13, 2014 #9


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    What on earth do you mean by the "ones" ?


    "Around 1" "Around 2" ?

    How can you average such wide ranging numbers, and why average them.

    Again: Please give much more meaningful detail regarding exactly what you have here.
  11. May 13, 2014 #10
    By ones I mean the bags. Around 1 are the value that round to one. And around 2 are the values that round to two. I averaged them so there is less numbers to common factor. And the remaining differences are the values that were not averaged.
  12. May 13, 2014 #11


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    I think I understand a little better, what the data stand for, and what you are trying to go with them.

    Once you sort (rearrange) your data, the only values you might ever consider averaging are those consecutive values with first differences close enough to zero. Determining what it means to be "close enough" depends on several factors.

    Bag #5, mass 156.414 g, and Bag #12, mass 156.374 g, likely contain an equal number of gummy bears .

    A lot depends upon the average mass of a bear in a large representative sample and how much variability there is in the mass of the bears.

    More to the point: Assuming the mass of a randomly chosen gummy bear is normally distributed, the ability to find a reasonable answer depends upon the mean of the distribution as well as the standard deviation.
  13. May 14, 2014 #12
    With that data, how can I find the mass of one gummy bear? Like how can I find the greatest common factor between these decimal numbers?
  14. May 14, 2014 #13
    This is the updated one.

    Attached Files:

  15. May 14, 2014 #14
    Can you please reply and give me a solution as soon as possible? I actually have to hand it in tomorrow.
  16. May 14, 2014 #15


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    I sorted the bag weights (you don't have to worry about the weight of the bag since that will cancel out when you take the differences), then sorted the pairwise differences and plotted a graph. I don't see any value that's terribly convincing. Maybe around 0.25? Or 0.57? 1.36? I suggest that either the gummy bears are too variable in weight, or you were putting too many per bag to get a useful answer (hundreds?), or the weighings were too inaccurate. Or some combination of the three.
    How many, roughly, do you think were in a typical bag?
  17. May 15, 2014 #16


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    I find that it's pretty difficult -- at least if you don't "cheat".

    I did find some references to the mass/weight of gummy bears. These were Haribo brand. Using this as a rough value, I can see that there must be quite a variance in the mass of individual Gummies.

    Back to how to get something from your data.

    Getting first differences from your data was a good place to start.

    It may make sense to average the values which are near zero. Actually average each group of consecutive values (the rearranged values) giving first differences of zero. For your data, that's only bags 1 & 8, bags 4 & 14, bags 12 & 5 -- & maybe bag 2 with the last 2, but #2 may be an "outlier".

    I only see two small differences between this and the earlier one, number-wise.
    A bag with mass 102.22 grams shows up. A bag with mass 162.22 grams disappears. That also changed sheet 2 somewhat.

    Hmmm . Any other typos in the data ?

    I've been messing with the data some.

    There appears to be too much variation in the mass of individual gummy bears, or in the weight of the bags holding them.

    If all were closer to having uniform mass, you could simply do something like a bar graph the first differences -- after sorting them. You then might be able to identify some fairly obvious step height.
  18. May 15, 2014 #17
    I already got it all figured out. Thanks for trying to help.
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