# Interesting errors

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

1. ### Betamale

14 divided by 3.......Cant do it, its not a real number
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 &pound;60 in a ratio of 8:3:1, how much does Jack get? ...answer 40:15:5

2. ### ian60New commenter

I came across this site a while ago
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. ### robyn147

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.

?! for real?

5. ### ian60New 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. ### arsinhNew commenter

Don't get it. Did you want your student to answer question 3 root 3 or not?
And ... chalk?!

7. ### pec01

Questions 1, 2, 3 ........10
Does not mean questions 1, 2, 3, & 10 !

8. ### Betamale

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. ### lilachardyStar commenter

And had it been 5/4, would her answer have been 4.5, I wonder!

10. ### Betamale

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...