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Arsey's C3 Edexcel 25th Jan 2013 Model Answers Thread (attached to first post)

Here are my model answers

The Core 3 paper wasn't anywhere near as bad as I expect some of you think it was. There were a couple of nightmare parts to questions but most of it was fairly standard and a well prepared candidate should have been able to achieve a decent mark out of 75.

Q1 Differentiation a) easy b) pretty easy - 7 marks (all okay)

Q2 Numerical methods a) easy (you don't need the bit I did in square brackets) b) easy - 8 marks (all okay)

Q3 Transforming graphs. This was a pretty easy question - 9 marks (all okay)

Q4 Trigonometry a) very easy, it is on virtually every paper b) This is pretty hard, understanding what to choose to lead to the maximum of p wasn't easy - 8 marks (4 easy, 4 hard)

Q5 Differentiation. Pretty easy, the proof was fairly easy - 11 marks (all okay)

Q6 i) Trigonometry i) I think this will be poorly answered but it is pretty easy ii) and b) easy - 11 marks (all okay)

Q7 Algebraic fractions and differentiation. Fairly easy - 12 marks (all okay)

Q8 Differentiation a) stupidly easy b) very hard - if you got this right, well done c) reasonable - 9 marks (5 okay - 4 hard)

So I think there are 8 hard marks that anyone taking the exam will have done well to get right.

In terms of boundaries I would be guessing at

52 = 70ums
59 = 80ums
66 = 90ums
73 = 100ums

(edited 11 years ago)

C3 Jan 13 Model red.pdf714.9KB

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Thanks ARSEY

Omg ive been waiting all morning i love arsey

Reply 3

otrivine

Original post by Arsey

Here are my model answers

hi arsey i got 1+sin45 ?

what do u predict the grade boundaries cause everyone got 2/11 not 2 for that question

Reply 4

thorn0123

Original post by Arsey

Here are my model answers

Arsey:

Would I get all the marks? Question 6i)

(sin(22.5) + cos(22.5))^2

Now I know this is straight forward but I went about it in a completely different way:

using the half angle formula:

cos^2(22.5) = \displaystyle\frac{cos(45)+1}{2}

cos(22.5) = \displaystyle\sqrt{\frac{cos(45)+1}{2}}

sin^2(22.5) = \displaystyle\frac{1-cos(45)}{2}

sin(22.5) = \displaystyle\sqrt{\frac{1-cos(45)}{2}}

expanding:

sin^2(22.5) + 2cos(22.5)(sin(22.5)) + cos^2(22.5)

then I sub in all the values found and get the answer to be

1 + \frac{\sqrt{2}}{2}

which is correct, but would I get all the marks?

I've shown every step in my working, and didn't use a calculator at all to get to the final step.

Reply 5

dank-knight

Argh for cos2theta +sintheta equals to one, i put as 2sintheta minus sintheta equals to one. NOOOOOO I lost all the marks for that.

Reply 6

bubblegummer

Original post by Arsey

Here are my model answers

thank you so much arsey! :smile:

wanna ask, if i got 594 pounds instead of 593 for the last question, will i still get full marks?

Reply 7

PlutoMars

Thanks alot arsey! :biggrin:

DDDDDD

Reply 8

thorn0123

Original post by bubblegummer

thank you so much arsey! :smile:

wanna ask, if i got 594 pounds instead of 593 for the last question, will i still get full marks?

I think you will lose 1 accuracy :frown:

Reply 9

mattd75

I loved that paper, found 8b and the sin22.5 one but solved them both in the final half hour so pretty sure I got at least 92% :smile:

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Reply 10

username937760

I completely missed the simple method for evaluating Q6a), and ended up butchering the method with a method that I am 90% sure isn’t the expected one, but also 90% sure that it’s completely valid. Would the following be awarded all of the marks?

Spoiler

(Note: May this be a lesson to us all to think about the question before launching into algebra.)

Reply 11

Arsey

Original post by otrivine

what do u think the grade boundaries will be? I am sure majority will have got 2/11 wrong well everyone in my school got 2/11.

what was difficult about Q2?

Reply 12

teen1234

I think this paper was hard purely because of exam cond. under pressure its sooo much more difficult to think around a problem like 8b. if it wasnt exam cond. i probably would have got it right...
If its 59 out of 75 for an A then Ill be over the moon

Reply 13

username937760

Original post by thorn0123

....

Glad I'm not the only one who completely missed the easy method for Q6. :tongue:

Reply 14

thorn0123

Original post by DJMayes

Spoiler

(Note: May this be a lesson to us all to think about the question before launching into algebra.)

haha

I done the exact same thing :biggrin:

- I walked out the exam thinking "I must be the only person to have gotten that question, it was so hard" Then to realise it was so easy :|

Reply 15

Arsey

Original post by DJMayes

Spoiler

(Note: May this be a lesson to us all to think about the question before launching into algebra.)

Very impressive and mental in equal measures. Well done.

Reply 16

otrivine

Original post by Arsey

what was difficult about Q2?

No the fraction one cause I assumed R=10 we just put that into the fraction to give 2/11

Reply 17

thorn0123

Original post by Arsey

what was difficult about Q2?

A lot of people thought maximum therefore cos(theta - 0.92...) = 1 and subbed that in, as it's usually like that.

Reply 18

thorn0123

Original post by Arsey

Very impressive and mental in equal measures. Well done.

Would we get all the marks?

Reply 19

Arsey

Original post by bubblegummer

thank you so much arsey! :smile:

wanna ask, if i got 594 pounds instead of 593 for the last question, will i still get full marks?

if you had the correct full answers and then just rounded incorrectly you may get full marks

it must be 2 marks for differentiating, method for substituting then an answer mark