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Interesting errors

Discussion in 'Mathematics' started by Betamale, Apr 9, 2011.

  1. 14 divided by 3.......Cant do it, its not a real number
    Perimeter ...answered in cm^2
    All answers to area questions answered in cm^2 despite the question being km/m/mm/ft etc
    7/7 = 0
    x^2 = 25 therefore x = 5 (from top set students)
    Triangle has a base of 6 and height of 7...area = 42...."so what s the area of a rectangle with a base of 6 and height of 7?" I as...."42"
    2^3 = 6...."Ok what is 2 x 2 x 2?" answer from kid "uhhh 8?" after finger counting...."Ok so what is 2 to the power of 3?"...."6?"
    "How do you divide fractions?" From a pupil who has been accepted on to do A level maths this year
    Jim, Jon and Jack share £60 in a ratio of 8:3:1, how much does Jack get? ...answer 40:15:5
     
  2. ian60

    ian60 New commenter

    I came across this site a while ago
    http://www.calculatorsoftware.co.uk/classicmistake/about.htm
    I printed out all the 'classic mistakes' laminated them and stuck them on the wall, they have attracted a lot of experience from all ages and abilities, and it's good to be able to point to them when someone inevitably commits a crime against mathematics.
    I know many others from these threads have used them from the comments on the site.
     
  3. The mean of 1,2,3,4,6,3,4,5,7 and 5 is not
    1+2+3+4+6+3+4+5+7 /10
    Because the average cannot be 23.7.
    Even if the calculator says so.

     
  4. harderfaster

    harderfaster New commenter

    ?! for real?
     
  5. ian60

    ian60 New commenter

    I'd written on the board :'Homework page 345 q 5/6'
    One student immediately asked "Do you mean all questions from 5 to 6, or just questions 5 and 6 only?"

    (Drops chalk whilst laughing)
     
  6. arsinh

    arsinh New commenter

    Don't get it. Did you want your student to answer question 3 root 3 or not?
    And ... chalk?!
     
  7. Questions 1, 2, 3 ........10
    Does not mean questions 1, 2, 3, & 10 !
     
  8. Be interesting if the topic had been about discrete/continuous data or strict inequalities.
    Chalk is good though
    Oh yes and they will get a C/B at GCSE
    I have top set student who told me my answer was wrong as I said 5/2
    She laughed as the teacher got it wrong "The answer is 2.5" as she has her lucky dip calculator in hand..............She will just miss an A grade based on previous units..
    Another pet hate is 1/3 is 30% and less annoying but still shocking "its 33%"
     
  9. lilachardy

    lilachardy Star commenter

    And had it been 5/4, would her answer have been 4.5, I wonder!
     
  10. No that wouldnt exist either, as you cant score 5 out of 4 in a test
    Failing that Im sure she would tell me Im wrong again as the 5th of April was last week, not this...
     

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