Math Is Fun Forum

Bob

Administrator

Registered: 2010-06-20

Posts: 10,583

Re: Edexcel Decision Maths 1 (General Help)

Q5a in D1 Jan 2010... it's an algorithm question.

Sorry,haven't got a set of papers and I cannot find this one on EdExcel's site.  Odd because they have every paper back to 2003.  every one but this one.

Have you got a link to it and the mark scheme?

Bob

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Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

zetafunc.

Guest

Re: Edexcel Decision Maths 1 (General Help)

No, use your calculator button by all means.  But remember your answer will only be as good as the poorest known value; so 2sf is the best you can say.

And there are other reasons that put the accuracy in doubt.

(i) Where was this circumference measured?  Trees usually get narrower as you go up.  Maybe that reason for wanting to know the diameter shouldn't be 'obscure'.

(ii)  And how circular is a tree anyway? 

(iii)  And bark is bumpy and fissured so the exact start and end point of the measurement is in doubt.

I expect that's why the physic's answers are given to a lower accuracy than you expected.  Physicists live in the real world.

One exercise that I have given to my classes was to draw any triangle, measure its angles and add them up.

For a while I would circulate, sorting out those who couldn't use a protractor properly, but eventually I'd be at the point of asking what totals they had got.

I usually got answers ranging from 178 to 182 degrees.

OK, what conclusion would you make?

One lad said "That the angles of a triangle add up to about 180°."

It was the first time any pupil had included the word 'about'.

But I had to admit, based on the experiment, it was an excellent conclusion!  What is absolute accuracy anyway?

I leave you to ponder this to whatever extent you like.  There is no expected answer so it is not necessary to post one.

Bob

Hmm, I don't know how to answer that question without reference to the uncertainty principle. We will always have error bars and estimates for the data. I suppose it would be too complicated to have a ±(error) in front of everything...

zetafunc.

Guest

Re: Edexcel Decision Maths 1 (General Help)

Sorry,haven't got a set of papers and I cannot find this one on EdExcel's site.  Odd because they have every paper back to 2003.  every one but this one.

Have you got a link to it and the mark scheme?

Bob

Hmm, that's weird, I just checked Edexcel's site and they definitely have it, both the question paper and mark scheme... maybe it wasn't working when you looked at it?

Also, on that same paper (if you can get it from Edexcel's website), I don't understand Q7d at all. If you can't get the paper, here's what it says:

" Let x be the number of standard cupboards, and y be the number of large cupboards. The capacity of a large cupboard is 40% greater than the capacity of a small cupboard. You wish to maximise the total capacity. Show that your objective can be expressed as "maximise 5x + 7y". "

I don't understand why it is 5x + 7y... why isn't it 7x + 5y? It doesn't appear to be a typo as you have to graph that for the next question too.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,583

Re: Edexcel Decision Maths 1 (General Help)

I'll have another try for the paper.  Jan 2010     D1   Correct?

A large cupboard, y, is 40% more than a standard, x.

So if the capacity of a standard is, let's say, C

x standards have capacity Cx

y large have a capacity 1.4Cy

=> total capacity = Cx + 1.4Cy  = constant times (5x + 7y)

So it is sufficient to maximise 5x + 7y

Bob

back when I find your other question.

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

zetafunc.

Guest

Re: Edexcel Decision Maths 1 (General Help)

Thanks for the quick response, that makes sense. I didn't think about letting there be a capacity C and using 1.4C instead of just 1.4*variable.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,583

Re: Edexcel Decision Maths 1 (General Help)

You are going to have to tell me where you are looking.

This is what the edExcel site says  (picture below)

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

zetafunc.

Guest

Re: Edexcel Decision Maths 1 (General Help)

Hmm, Google "gce maths 2008" and click on the very first link at the top.

Bob

Administrator

Registered: 2010-06-20

Posts: 10,583

Re: Edexcel Decision Maths 1 (General Help)

hi zetafunc,

Arhhh!  That worked.  Curious though.  I started on the homepage and worked through to GCE maths, then past papers etc.  That led to a completely different page.

My answer:

I put 25000, 0, 17000, yes, blank on my first line then

blank, 3400, 7000, yes, blank on the  next

blank, 4450, -5000, no, 4450 on my last line.

Looking at the way they are allocating the marks, I think they have missed lines for the markers purely to make it easier to explain what marks for what.  There is no reason at all why you shouldn't do as I have done.

The person who creates the mark scheme has to show the expected answers and try to cover all possibilities for how a candidate will answer.

The mark scheme is written for markers not candidates;  it is not a model answer for the question and you are reading too much into it.

As I know from the little bit of marking I did (one set of C2 papers), candidates manage to find many ways to present their work.  The overriding principle for markers is that correct maths in answer to the question should be rewarded.  Just keep that in mind and do your best!

Hope that clears it up.

Bob

---

Children are not defined by school ...........The Fonz
You cannot teach a man anything;  you can only help him find it within himself..........Galileo Galilei
Sometimes I deliberately make mistakes, just to test you!  …………….Bob

zetafunc.

Guest

Re: Edexcel Decision Maths 1 (General Help)

Hi, thanks for clearing that up! So it turns out that I can do them on the same lines. Great!