Basic math.. Who knows it?

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  • susannamarie
    susannamarie Posts: 2,148 Member
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    what are you getting on a calculator?
    i've used 3 calculators and they say 3
    You've done it incorrectly 3 times!

    i don't know how to use a calculator then either lol

    Most 4-function calculators cannot do order of operations correctly. If you use a scientific calculator which can evaluate multiple operations at once (for a free online one, go to wolframalpha.com), you will get the correct answer of 7.
  • si_puedo
    si_puedo Posts: 138 Member
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    3
  • jnhu72
    jnhu72 Posts: 558 Member
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    7!
  • dovesgate
    dovesgate Posts: 894 Member
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    This thread makes me very sad by the way... yikes....

    Me too. I feel utterly stoopid now. :huh: :noway: :grumble: :embarassed: :frown: :sad:
  • love22step
    love22step Posts: 1,103 Member
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    7

    Please excuse my dear Aunt Sally (PEMDAS)

    Order of Operations: Parentheses, Exponents, Multiply, Divide, Add, Subtract
  • Dan112358
    Dan112358 Posts: 525 Member
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    Blerg. Time to start drinking.
  • mommared53
    mommared53 Posts: 9,543 Member
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    Well, in my defense, (and my answer was 12 btw) I'm 58 so it's been a long, long time since I studied basic math. Even back in grade school I was terrible at math and I don't remember anything about Aunt Sally. Now spelling on the other hand . . .
  • Jorra
    Jorra Posts: 3,338 Member
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    some of you need to lighten up
    i don't think answers to this math equation predict the fate of humanity

    Maybe math illiteracy in the general public won't destroy humanity. However, education is my life's passion, and it's seriously depressing me how it has failed so many.
  • susannamarie
    susannamarie Posts: 2,148 Member
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    If you use simple math like you learn in elementary school, there is no negative numbers. it would go 9 - 5 = 4 + 5 = 9 X 0 = 0 + 3 = 3. This is why my first anwser was 3. Hmmm

    The other problem (and not to be mean, just picking on your quote because this is a common error) is that you are writing equals between things that are not equal. 9-4 is not equal to 4+5. This causes no end of problems in more advanced math classes -- where people actually need to work with strings of equalities.

    So a shout-out to the elementary teachers out there -- please don't teach your students to write this. We have to spend so much time un-teaching it at university.
  • treetop57
    treetop57 Posts: 1,578 Member
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    Most 4-function calculators cannot do order of operations correctly. If you use a scientific calculator which can evaluate multiple operations at once (for a free online one, go to wolframalpha.com), you will get the correct answer of 7.

    To my surprise the windows calculator gets this problem right. I'd never trust a calculator with something like this though so I didn't know it would get it right!
  • k0nfyo0zed
    k0nfyo0zed Posts: 313 Member
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    posted some explanations on the original post.

    thank you to everyone who answered 7, or at least didn't defend an incorrect answer with incorrect processes. :)
  • Nopedotjpeg
    Nopedotjpeg Posts: 1,806 Member
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    The 7 year old me feels pretty good about himself right now.
    However, I probably have forgotten all the algebra I learned a few years ago so I guess everyone has things that aren't their thing.
  • susannamarie
    susannamarie Posts: 2,148 Member
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    Most 4-function calculators cannot do order of operations correctly. If you use a scientific calculator which can evaluate multiple operations at once (for a free online one, go to wolframalpha.com), you will get the correct answer of 7.

    To my surprise the windows calculator gets this problem right. I'd never trust a calculator with something like this though so I didn't know it would get it right!

    Not sure about your version of windows -- in my version (older) it does it correctly in scientific mode and incorrectly in standard mode, which is just wild :D
  • PayneAS
    PayneAS Posts: 669 Member
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    basicmath.jpg

    Please restore my faith in humanity...

    I know the thing says "comment with your answer only" but I would like that to say "show your work!"

    Remember elementary and middle school?

    (i apologize if i have brought back repressed memories of creepy math teachers)

    (big hint: the answer is not 0, 1 or 3... or 9 or 12!) here's why:


    AFTER 6 PAGES I'M EDITING TO ADD THIS IN... SPOILERS? :)

    PEMDAS is the order of operations. parentheses, exponents, multiplication, division, addition and subtraction.

    so, you do the multiplication first 5x0=0

    that makes the problem 9-5+3.

    when you get to addition and subtraction you work the problem left to right, 9-5 = 4. then 4+3 = 7.

    IF you chose to do addition first, you need to be sure to take the symbol in front of the number with it, thus making the problem 9+ (-5) + 3 which, is still 7.

    it's not 0 because the whole equation isn't multiplied by 0, only 5. for it to be zero it would have to read (9-5+5-3) x 0

    it's not 1, because when you do the addition first, it's not 5+3, it's -5+3 which is -2, and 9 + (-2) is 7.

    it's not 3, because you don't do the problem left to right, you have to do the multiplication first. for the answer to be three it would have to read (9-5+5) x 0 + 3

    it's not 9 because you can't cancel out the -5+5 without doing the multiplication first.

    and answers of 7 make me happy. :)

    (clear?)

    PEDMAS

    9 - 5 + (5 x 0) + 3

    9 - 5 + 0 + 3

    9 - (5 + 0 + 3)

    9 - 8 = 1

    Edit: And yes I added the parentheses for clarification.
  • NU2U
    NU2U Posts: 659 Member
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    I think I just burned 50 calories..........:bigsmile:
  • treetop57
    treetop57 Posts: 1,578 Member
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    Most 4-function calculators cannot do order of operations correctly. If you use a scientific calculator which can evaluate multiple operations at once (for a free online one, go to wolframalpha.com), you will get the correct answer of 7.

    To my surprise the windows calculator gets this problem right. I'd never trust a calculator with something like this though so I didn't know it would get it right!

    Not sure about your version of windows -- in my version (older) it does it correctly in scientific mode and incorrectly in standard mode, which is just wild :D

    Sure enough. Same here. I never would have predicted that either!
  • k0nfyo0zed
    k0nfyo0zed Posts: 313 Member
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    sigh. it doesn't become 9-8... you don't add 5+3 you have to add -5 + 3...
  • Frayed_Ends
    Frayed_Ends Posts: 54
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    some of you need to lighten up
    i don't think answers to this math equation predict the fate of humanity

    Oh man am I going to laugh when the fate of humanity comes down to having 9-5+5x0+3 rounds of ammunition per 7 zombies.
  • susannamarie
    susannamarie Posts: 2,148 Member
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    PEDMAS

    9 - 5 + (5 x 0) + 3

    9 - 5 + 0 + 3

    9 - (5 + 0 + 3)

    9 - 8 = 1

    This is incorrect -- addition and subtraction are done at the same time, left to right -- because subtraction is really just adding the negative. It really could be written as PE(MD)(AS) for clarity.
  • Elizabeth_C34
    Elizabeth_C34 Posts: 6,376 Member
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    This thread is just getting worse and worse...

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