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# OCR C4 (not mei) 18th June 2013 revision watch

1. (Original post by a10)
I don't think we'll lose marks for it, if we do that's very harsh.
Unfortunately, I think you do, I lost a mark for that in my mock

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2. (Original post by Namige)
Does anyone know how they worked out x=0.1 for q10? I just guessed 0.1 and it gave me the correct fraction lol
I'm guessing that you put it into the unexpanded version? If you put it in the expanded version it gave 0.176 or something like that.
3. (Original post by HypErTwisT)
sin(173) = sin(9)
or whatever the values were, they are equal so if you did the rest right your volume should be fine. I left it as 171 as well....
I don't know, the answer everyone gave for the volume didn't ring any bells. I probably messed it up in some other way...
4. On Q4 with the stationary values. I got all the x-values right but I misread and did not realise they wanted co-ordinates (i.e. I didn't sub in for the y-values). How many marks do you think I would lose out of the 6? I imagine no more than 2 surely.

Oh and The volume of the pyramid is another thing that is worrying me. I think I got the volume of the sphere, but I left it in terms of Pi (fraction * Pi).

This paper was more challenging than previous papers, I have a feeling 80 UMS will be around 55 and 90 therefore around 62/63, The Jan 12 barrier was 55 for an A and to be honest I think this paper was harder than that one. So I wouldn't be surprised if it was like 52 for an A. Didn't get the one marker at the end either. Damn I forgot about |x| < 1
5. (Original post by tooambitious)
Unfortunately, I think you do, I lost a mark for that in my mock

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yeah but that may have been your teacher, and you didn't have to sub in any limits so I don't think marks will be taken away but anyway i'll just have to ask Mr M when he posts the markscheme!
6. (Original post by strikerextreme)
which questions did you find hard jiraiya ?

i was thrown off by q10)

i think those kind of expansion questions come in aqa past papers
I reckon lost 3 marks on the last question in total and an additional 3 from the other questions. So 6 lost in total, so far....
7. (Original post by Namige)
Does anyone know how they worked out x=0.1 for q10? I just guessed 0.1 and it gave me the correct fraction lol
Mine wasn't a guess. I realised that it was 100/93, so 1-x had to be a multiple of 9. That made me try 0.1/0.93, which came out as 100/729
8. Well my chance of an A* has gone put hopefully i scraped an A overall. I know I got the substitution all muddled up and so 3-4 marks dropped there. I got the pyramid question wrong 3 more marks dropped. The inversely proportional all wrong as I just did proportional so 7 marks dropped there. I didn't simplify fully the differential equation so thats another mark lost. And i couldnt do the last 2 parts of the last question so that is 5 marks dropped. So thats like 19 marks dropped at least ahhhhh!!!!!!!!

I hope you all get the grades you wanted, off to revise chemistry now for my last exam tomorrow
9. (Original post by Maid Marian)
All the things I did wrong:

-Forgot cos x = 0. I am an idiot.
-Didn't integrate tan2x properly. I am thick.
-Didn't know what inversely proportional meant. I really am thick.
-That means I got the whole of q8 wrong.
-Worked out the obtuse instead of acute angle, therefore I got the volume wrong.
-I don't think I got t=1 .... Sigh.
-That means I got q9 all wrong. More marks down the drain.
-Couldn't understand number 10 at all. No marks there.

Yeah. I really am beating myself up about this ... I need an A in maths to get into uni!!!!!!!
the obtuse angle gives you the same as the acute angle. Sin(x)=sin(180-x).
10. (Original post by JASApplications)
It does. 2.7^2/3 = 1.94 and 4.86^2/3 = 2.87
I dont think you can just split it up like that.

Imagine we have z^2=x^2 +y^2
z = (x^2 +y^2)^1/2

It does not equal X + Y because if you then do (x+y)^2 you get X^2 + y^2 +2xy which is not the original
11. Reckon I lost 6-8 marks on this paper hoping my C3 will get me in the A* range.
12. Does anyone know if e.c.f can give you 'full' marks for a question?

By that I mean, stupidly messed up the angle in the pyramid by putting 47 rather than 49 into my calculator as the result of the dot product. This meant my angle was wrong.

My method for the last bit I did correctly, and wrote it out step by step, but obviously got the wrong answer since my angle was wrong. Would I still get 3 marks since I did do 1/3 * 1/2 ab*sin(c) [using my c]* mod[AD].
13. (Original post by Maid Marian)
All the things I did wrong:

-Forgot cos x = 0. I am an idiot.
-Didn't integrate tan2x properly. I am thick.
-Didn't know what inversely proportional meant. I really am thick.
-That means I got the whole of q8 wrong.
-Worked out the obtuse instead of acute angle, therefore I got the volume wrong.
-I don't think I got t=1 .... Sigh.
-That means I got q9 all wrong. More marks down the drain.
-Couldn't understand number 10 at all. No marks there.

Yeah. I really am beating myself up about this ... I need an A in maths to get into uni!!!!!!!
If it makes you feel better I got my partial fractions drastically wrong...and they're not even hard. Also banking on an A for uni!
14. (Original post by sj_1995)
Does anyone know if e.c.f can give you 'full' marks for a question?

By that I mean, stupidly messed up the angle in the pyramid by putting 47 rather than 49 into my calculator as the result of the dot product. This meant my angle was wrong.

My method for the last bit I did correctly, and wrote it out step by step, but obviously got the wrong answer since my angle was wrong. Would I still get 3 marks since I did do 1/3 * 1/2 ab*sin(c) [using my c]* mod[AD].
I think you can still get all the working marks but not the answer mark, so you would lose 1 mark for each subsequent question, but Im not 100% sure

15. for this question i solved the diff equation but my answer wasnt expressed as r=

how many marks would i lose ?
i got the c value
16. question didnt ask for acute angle so i guess acute is ok right!!!??
17. (Original post by Ursin)
If it makes you feel better I got my partial fractions drastically wrong...and they're not even hard. Also banking on an A for uni!

I'm just sooooooo angry with myself, I'm nearly crying I made myself look like I've never done a c4 paper before ... so frustrating.
18. (Original post by mrmccarl)
im just so shocked that t=1 not -1. how did i mess up such a basic question (((((
I know!! I did the same thing
silly me !!
19. (Original post by Alex Newton)
I think you can still get all the working marks but not the answer mark, so you would lose 1 mark for each subsequent question, but Im not 100% sure
Just seen this on a previous mark sheme;
"The abbreviation ft implies that the A or B mark indicated is allowed for work correctly following on from previously incorrect results. Otherwise, A and B marks are given for correct work only — differences in notation are of course permitted. A (accuracy) marks are not given for answers obtained from incorrect working. When A or B marks are awarded for work at an intermediate stage of a solution, there may be various alternatives that are equally acceptable. In such cases, exactly what is acceptable will be detailed in the mark scheme rationale. If this is not the case please consult your Team Leader.

Sometimes the answer to one part of a question is used in a later part of the same question. In this case, A marks will often be ‘follow
through’. In such cases you must ensure that you refer back to the answer of the previous part question even if this is not shown within the
image zone. You may find it easier to mark follow through questions candidate-by-candidate rather than question-by-question.2"

That gives me some hope!!
20. (Original post by strikerextreme)

for this question i solved the diff equation but my answer wasnt expressed as r=

how many marks would i lose ?
i got the c value
It didn't explicitly say form r=f(t) do it should be fine.
As long as r was one side and t on the other you should be ok

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