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Questioning of pi

  1. Jan 15, 2015 #1
    Well I'm super confused about this cause the trust is balanced.
    here's my question:

    which is right:

    3.14159265359 blah blah blah
    -supported by google
    -supported by http://www.quora.com/Why-is-PI-22-7 [Broken]
    also says that 22/7 is an approximation


    22/7 which is 3.14285714286(I don't know extended or not.)
    -supported by my maths teacher
    -supported by my fat ol' friend
    Last edited by a moderator: May 7, 2017
  2. jcsd
  3. Jan 15, 2015 #2


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    -supported by mathematics, which is the only thing that really counts.

    Which is not a very good approximation, as you can see compared to the value you wrote above.
    Last edited by a moderator: May 7, 2017
  4. Jan 15, 2015 #3


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    PI isn't here but like these, 22 / 7 is just an approximation.
    Source: http://xkcd.com/1047/

  5. Jan 15, 2015 #4


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    If your teacher thinks that pi is exactly equal to 22/7, then I'm worried for your class.

    Google is correct. Pi is approximately equal to 22/7, but not exactly equal.
  6. Jan 15, 2015 #5


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    Here's a better approximation for PI - 355 / 113. It's good to 6 decimal places but like 22 / 7, it isn't exactly equal to PI.
  7. Jan 15, 2015 #6
    She says that 22/7 is the correct value of pi and 3.141 blah blah is just an approximation.
  8. Jan 15, 2015 #7


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    Wow. ?:) I'm with Mentallic on this. Sorry for your class if that's what she is teaching.
  9. Jan 15, 2015 #8
    Then shall I conclude that my maths teacher is wrong along eith my fatso friend.
  10. Jan 15, 2015 #9
    Alsi it wasn't taught a simple algaebric expression was given to break down which was
    As I like pi strarted all about pi and my friend calculated 22/7 and then a debate then asking the teacher (asking for a fez).
  11. Jan 15, 2015 #10


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    The problem is that she is teaching this to people. It would be great if you could get her to create an account and post her logic here. There would be plenty of people who would be happy to explain it to her. :)
  12. Jan 15, 2015 #11


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    Here's an interesting take on this:

    ##\pi = \frac{22}{7} - \int_{0}^{1} \frac{x^4(1-x)^4}{1+x^2} dx##
  13. Jan 15, 2015 #12

    Quantum Defect

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  14. Jan 15, 2015 #13


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    Since your teacher is not here to defend him- or her-self, did he or she say that "pi is equal to 22/7" or "It is better to use 22/7 for pi than 3.14"?
  15. Jan 15, 2015 #14
    Let me quote my teacher :

    "22/7 is the exact value of pi and 3.141 is an approximation"
    (I'm I getting her wrong")
  16. Jan 15, 2015 #15
    She is right about the second part, but the first is also an approximation.

    Mr.maniac, I don't know you so please don't be offended by what I say/ask: Is that actually an exact quote or is that what you think you remember from the middle of an argument. I only ask this because I teach, and while I have definitely misspoken, I am more often misquoted.

    Is it possible that this is on a standardized test that explicitly told you to use the value 3.14 or 22/7 for ##\pi## in your calculations? If this is the case, you may have misunderstood her telling you to use that value. If there wasn't some strange context (eg. she preceded it by saying, "the next statement I make is false" :oldsmile:), she was wrong.

    Also, in these sorts of debates (math debates) wikipedia is usually pretty reliable.
  17. Jan 15, 2015 #16


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    22/7 ##\approx## 3.142857. Both 22/7 and 3.141 are approximations to the actual value of ##\pi##. According to wikipedia, the first 50 digits of ##\pi## are 3.14159265358979323846264338327950288419716939937510 (http://en.wikipedia.org/wiki/Pi). Clearly 3.141 is a better approximation than 22/7.
    Are you trying to say "Am I getting her wrong?"
  18. Jan 16, 2015 #17
    (Yes it's am I getting her wrong)
    And DrewD they are the exact words of my teacher.
  19. Jan 16, 2015 #18
    And she is saying 3.141 blah blah is wrong
  20. Jan 16, 2015 #19


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    Please see Mark44's post #16 above.
    22/7 AND 3.1416 are both approximations. He has listed the correct value of Pi to 50 digits.

    If your teacher is saying anything otherwise, she is wrong.
  21. Jan 16, 2015 #20
    Well that's unfortunate. I would nicely do what she wants in class but carefully check to be sure it is correct. If it is incorrect, ask her and if she doesn't realize the mistake, keep track of it and let an administrator know. Well, that's not actually what I would have done, but it is the most likely way to actually accomplish something.
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