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

1. Any Idea how many marks you would lose on question 4 for only putting the X values sadly didn't read they wanted co-ordinates
Any Idea how many marks you would lose on question 4 for only putting the X values sadly didn't read they wanted co-ordinates
Same here, I'd like to know this also! I want to see the wording of that question, I'm not one to make such a silly error normally
3. (Original post by Mr M)
drop 1
How many marks is not converting an integral in 'u' form back into 'x' form? where u is the substitution
4. I'm proposing
A = 55
B = 49
C = 42
D= 37
E = 32
now because people say that me proposing A=57 was too high
anyone agree?
5. (Original post by XingBairong)
I'm proposing
A = 55
B = 49
C = 42
D= 37
E = 32
now because people say that me proposing A=57 was too high
anyone agree?
possibly even lower.
6. (Original post by Namige)
How many marks is not converting an integral in 'u' form back into 'x' form? where u is the substitution
I got the same problem as u how many marks do u reckon we will get?

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7. (Original post by XingBairong)
I'm proposing
A = 55
B = 49
C = 42
D= 37
E = 32
now because people say that me proposing A=57 was too high
anyone agree?
I reckon take away 4 from all of them and that'll be about right - I did most of the past papers back to 2006 and it was easily the hardest one.
8. (Original post by stirkee)
possibly even lower.
well, I'd have liked it to be like 51 for an A like in summer 2011 :L
but I don't wanna be too optimistic
9. (Original post by Mr M)
I've looked now. Are there any questions that people are unsure about and would like a second opinion on?
How many marks would I lose for these mistakes?:
In Question 4 I divided by cos(x) so lost the (pi/2,0) stationary point.
In Question 5 part ii) I put my answer as 0.5ln(3^0.5)
In Question 7 part iii) I forgot to multiply by 1/3 so got an answer of 28.0
In Question 8 i) I found dr/dt as k/r^0.5 and found k to be 81/25, then (2/3)r^(3/2) = kt + c as the integral and found c to be 9/5, but when finding t in terms of r I squared and then cube rooted the terms individually.

Would I get any marks for the following?:
In 8 ii) I only had time to write (4/3)(pi)(1.94)^2= without finding an answer.
In 10 i) I put values of x into the equations and saw that they were roughly equal instead of doing the expansion.

Thankyou in advance, you are a complete legend and you deserve to be paid for what you do on here
10. Hi Mr M,

Could you possibly do the show part of question 10 (iii) on here as I spent ages looking at it in the exam but never managed a sufficient proof! Also, could you do the pyramid question please?

Thanks!
11. (Original post by mrmccarl)
i feel unbelievably depressed right now :-(. someone cheer me up!!! i have chem unit 4 tomorrow as well ((
I think lots of us are depressed! But everything will turn out alright. The best thing you can do is just put this exam in the past and focus on your next one.
12. (Original post by Mr M (jr))
Actually, there's nothing wrong with this; your k is just 1/(most other students' k). The equation, although different, will still be correct.
Thank you but I have realised I made another silly mistake,
When I integrated 1/k I stupidly put Kt, so when I subbed in the t/r value and the k value I found from the dr/dt equation, I got the final equation wrong, how many marks would I loose?
For part ii) would they mark it based on your equation to part i)

tha
13. What page is the unofficial mark scheme on?
14. Mr M,

5ii) I completely forgot how to integrate tan2x. I ended up integrating to 1/2tan2x (I know that's completely wrong) and then I applied the limits and got a random answer! - Do you think I'll get 1 mark for applying the limits?

7i) I got the correct angle 171 degrees but then went on to find the acute angle (8.68 degrees). Will I lose any marks? I read somewhere that when they see the correct answer, they ignore following working?

7ii) I worked out AD to be root56. And then I did 1/3 x root91 x root27 x root56 to get 123.6. How many marks do you think I'd get?

8i), I got the correct answer but didn't leave it as
I took the root by power 3/2 of the things on the right hand side so I got r = 2.87t + 1.94
Lose 1 mark?

8ii) I didn't use the exact value or r. I used r = 1.94 so I got 30.6 instead of 30.5. Would I still get full marks?

Thanks a lot!
15. (Original post by JASApplications)
It does. 2.7^2/3 = 1.94 and 4.86^2/3 = 2.87
I'm certain it doesn't...for example (3x+2)^2 = 9x^2 + 12x + 4 it does not equal 9x+4

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16. can you tell me how many marks I'd lose:

4: only gave 2 SPs (forgot the cosx = 0 one)

6: got the correct answer in terms of U but forgot to change it back to x

8: said dr/dt = k root r... subsequently got that answer and the next one wrong

Urgh stupid mistakes ;l
17. (Original post by JASApplications)
Mr M,

5ii) I completely forgot how to integrate tan2x. I ended up integrating to 1/2tan2x (I know that's completely wrong) and then I applied the limits and got a random answer! - Do you think I'll get 1 mark for applying the limits?

7i) I got the correct angle 171 degrees but then went on to find the acute angle (8.68 degrees). Will I lose any marks? I read somewhere that when they see the correct answer, they ignore following working?

7ii) I worked out AD to be root56. And then I did 1/3 x root91 x root27 x root56 to get 123.6. How many marks do you think I'd get?

8i), I got the correct answer but didn't leave it as
I took the root by power 3/2 of the things on the right hand side so I got r = 2.87t + 1.94
Lose 1 mark?

8ii) I didn't use the exact value or r. I used r = 1.94 so I got 30.6 instead of 30.5. Would I still get full marks?

Thanks a lot!
7ii) I did t the same and I'm guessing 0 unless they give you one for timing it by the right height? 0 or 1 but more likely 0 :L
18. Did anyone else find that for the first vector question that they didn't give you enough room?
At the start of the exam when they got to that question loads of people were asking for extra paper.
19. I think the paper included some stuff that was a bit different but a harder paper means easier grade boundaries at the top end.
I did a few silly mistakes included Q2 and the parametric question but I think the A boundary will be 51/52 as the single maths people were saying it was the worst paper ever and were crying. Some said they only answered 6 marks which was confusing.
Hopefully 58 for A*!

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20. Most people In my school struggled with this on the whole. Easily the hardest C4 paper ive done. Thinking about 52 for the A?

Nice to see people thinking the same. Think ive dropped 18-20 marks. Made some horrible mistakes

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