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#1 2013-12-09 06:44:40

silverpuma
Member
Registered: 2011-06-19
Posts: 72

Teacher marks answer wrong but I cannot understand why?

Below is the group of questions on "Transformations" my son (and me with him) is learning you will see part (c) is marked wrong.  Thats not a problem, mistakes is how we learn its just I'm so daft I can't understand why we are wrong and I want to understand, please help.   

(a) What translation has taken K to K’ in the diagram below?
My Son’s Answer:…..7, 6…..marked correct
   
(b) What translation has taken V to V’ in the diagram below?
My Son’s Answer:…..5, -5…..marked correct
   
(c) What two individual translations parallel to the x-axis and the y-axis respectively would replace the single translation from V to V’?
My Son’s answer:….5,0 and then 0,-5…..marked wrong

The teachers answer is Translation  y = x





PS:   Im learning Maths alongside my son to try to help him  I find maths really interesting and love this new learning curve for me but it does not come easy as I have no, zero, academic qualifications just lots of uneducated enthusiasm so please go easy on me…….:-)

Last edited by silverpuma (2013-12-10 15:22:59)


“Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened.”  ―  Winston Churchill

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#2 2013-12-09 06:54:45

silverpuma
Member
Registered: 2011-06-19
Posts: 72

Re: Teacher marks answer wrong but I cannot understand why?

The missing image.....:-)

View Image: WP_20131209_001-001.jpg

“Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened.”  ―  Winston Churchill

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#3 2013-12-09 07:02:30

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,469

Re: Teacher marks answer wrong but I cannot understand why?

hi silverpuma

Thanks for the diagram.  I'm treble puzzled by this.

Firstly did 7,6 really get marked as "correct" ? Or is that a typo ?

The correct answer is

I'm happy with the next answer.

And with your final answer.

A translation of y=x is not an answer to this question:

(c) What two individual translations parallel to the x-axis and the y-axis respectively would replace the single translation from V to V’?

(i) This is not two translations.

(ii) It's not even one translation.  This is not how translations are written.  You could have a translation in the direction of the line y = x but this isn't.  And you'd still have to say how much in that direction.

I did wonder if the teacher meant for you to find another transformation altogether such as a reflection.  But that won't work either as the shape hasn't flipped over; it's the same way round and that dictates a translation.

There are in fact an infinite number of translation pairs but only yours obeys the requirements about directions.  Here is another pair if we ignore the direction requirement.

I wonder if the teacher had an answer sheet and just looked at the wrong answer.  dunno

What age is your son and what course is this for ?

There are some good pages on transformation geometry on the main MathsIsFun website:

http://www.mathsisfun.com/geometry/translation.html

Bob

Last edited by bob bundy (2013-12-09 07:39:48)


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#4 2013-12-09 08:23:43

silverpuma
Member
Registered: 2011-06-19
Posts: 72

Re: Teacher marks answer wrong but I cannot understand why?

Bob, thank you so much for the detailed answer and it's good to know my son understood and answered the question correctly.
You are correct about question (a) I made a typo copying my son's answer,  7,0 is the correct answer. 

The teacher is really excellent (strict and that's no bad thing today:-)) so this is in no way a slight on the teacher at all.   Teachers are under so much pressure with result league tables etc I have a lot of sympathy for them and mistakes happen.  My middle name I think is "Mistake" I am so prone to silly slip-ups myself sometimes.....LOL

Thanks again for your help.....

Last edited by silverpuma (2013-12-15 11:03:00)


“Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened.”  ―  Winston Churchill

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#5 2013-12-09 10:44:46

bob bundy
Moderator
Registered: 2010-06-20
Posts: 6,469

Re: Teacher marks answer wrong but I cannot understand why?

hi silverpuma

I was a teacher in UK state schools for 37 years so I'm very aware of the pressures and my sympathies are with this lady too.  But correct maths shouldn't be decided by democratic vote, or we'd still be believing the Sun goes round the Earth and that pi = 3.
http://en.wikipedia.org/wiki/Indiana_Pi_Bill

I would hope that she has a set of correct answers and does a check on the answer that is being offered.  Some of the greatest mathematicians have been, at some time, in a minority of one and yet, in time, been shown to be correct.  Has your son got the courage to question an answer determined that way?  I always had the greatest respect for any pupil that was prepared to argue their case against the majority.

But I also understand that it's a tough thing to suggest.  So plan B is to come here and ask for our opinion.  If you're wrong, someone will try to explain why, and if you're right, then it will save you a lot of time struggling to square the circle.

Bob


You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei

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#6 2013-12-09 15:22:06

silverpuma
Member
Registered: 2011-06-19
Posts: 72

Re: Teacher marks answer wrong but I cannot understand why?

Once again Bob thanks for your measured and thoughtful answer.  My son would not like to query this error he is on the shy end of things and I'm not a very confident person myself regarding anything academic being a secondary school student with at best between a C and C+ average.  But I will eagerly take up your advice and pepper you and the good folks here as and when I need some clarification.   My son seems to have a natural touch (combined with hard work and a desire to get every question right) with numbers, although I do not, nevertheless I'm enjoying the journey alongside him encouraging him and discovering a road I never thought I could be or would be interested in.....Maths.

I'm smiling as I write as I think back 43 years ago, opening my 11+ results envelope on a Saturday morning, reading I failed and then without a hint of distress went back up to my bed for a few more hours sleep. Ah well, if only adult life could be lived in a free, stressless  "take it in your stride" like I had all those years ago.  I can dream...:-)

There are a few questions from a few weeks ago that may fall into the same category as the one we have been looking at but it may be me mistaking this time.  I'll post them when I search them out.  Thanks......

Last edited by silverpuma (2013-12-09 15:57:48)


“Men occasionally stumble over the truth, but most of them pick themselves up and hurry off as if nothing ever happened.”  ―  Winston Churchill

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