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# Mr M's OCR (not OCR MEI) Core 3 Answers June 2012

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1. Mr M's OCR (not OCR MEI) Core 3 Answers June 2012

1. and (5 marks)

2. (i) Show 261 (3 marks)

(ii) 361 (3 marks)

3. (i) Show tan theta = 6 (3 marks)

(ii) (a) (2 marks)

(b) (2 marks)

4. (a) Show integral = 24 (4 marks)

(b) (4 marks)

5. (i) Show one real root (3 marks)

(ii) (a) 3 and 4 (3 marks)

(b) 3.24 (4 marks)

6. (i) 12.17 (4 marks)

(ii) 0.183 cubic metres per hour (3 marks)

7. a = 4 and x = -0.5 (7 marks)

8. (i) (3 marks)

(ii) (a) -64.7 degs and 138 degs (4 marks)

(b) k = 8 and c = 3 (4 marks)

9. (i) Show derivative (3 marks)

(ii) (6 marks)

(iii) (2 marks)
2. thanks again!
3. Thanks
4. Mr M, for question 9(ii) for some reason I differentiated ln(2y) instead of integrating (I was trying to integrate but I was just being retarded), and got my answer from there. Will I get a mark?

EDIT: Btw thanks a lot for the solutions!
5. Mr M 4(b) I accidently messed up when multiplying out the brackets but integrated the terms are everything fine - how many marks would I get for that?

hope the after school meeting was...fun?
6. Oh and would it be okay for 4(b) to give my answer as e(0.5e+4)-0.5? Thanks
7. (Original post by tahseen1995)
Mr M, for question 9(ii) for some reason I differentiated ln(2y) instead of integrating (I was trying to integrate but I was just being retarded), and got my answer from there. Will I get a mark?

EDIT: Btw thanks a lot for the solutions!
I can't say from what you have told me - it doesn't sound hopeful!
8. How many marks would I drop if I put 4/3 < x < 6 for q1
, and for using g^1(x) instead of g(x) for the second part of 7?
9. (Original post by tahseen1995)
Oh and would it be okay for 4(b) to give my answer as e(0.5e+4)-0.5? Thanks
yes
10. (Original post by Mr M)
Mr M's OCR (not OCR MEI) Core 3 Answers June 2012
Mr. M, for 9ii) (the 6 mark question), I did everything correctly up till the point where we had to calculate the lower bound. For some reason, because i'm a dog I differentiated rather than just plugging x=0 into f(x), hence I integrated with lower bound 1, instead of lower bound 1/2. All the steps in the integration were correct, but my final answer would be wrong since the lower limit I subbed in was wrong. How many marks would I lose in your opinion?
11. (Original post by Doctor.)
Mr M 4(b) I accidently messed up when multiplying out the brackets but integrated the terms are everything fine - how many marks would I get for that?

hope the after school meeting was...fun?
It was mercifully brief. I did maths and pretended to listen.

probably 2 marks
12. I can't remember what I put for 4b, can anyone remember the question? Thanks.
13. (Original post by Tukazoar)
How many marks would I drop if I put 4/3 < x < 6 for q1
, and for using g^1(x) instead of g(x) for the second part of 7?
drop 1 mark and drop 3 marks probably
14. (Original post by Mr M)
I can't say from what you have told me - it doesn't sound hopeful!
What I meant is I correctly rearranged the equation to get pi times the integral of y=ln(2x) with limits of 1/2e^(4) and 1/2, but instead of using part (i) of question 9 to find the integral of ln(2x) I integrated ln(2x) to 1/x (I panicked due to lack of time) and went from there.

I was wondering if would at least get a mark for correctly rearranging the equation and realising the the area of the shaded region rotated about the y axis would be the integral of ln(2x) within limits of 1/2e^(4) and 1/2 multiplied by pi.

...did I make sense?

lol thank you
15. I'm off home now but will answer some more questions later (in about one hour).
16. (Original post by Doctor.)
Mr M 4(b) I accidently messed up when multiplying out the brackets but integrated the terms are everything fine - how many marks would I get for that?

hope the after school meeting was...fun?

(Original post by tahseen1995)
Mr M, for question 9(ii) for some reason I differentiated ln(2y) instead of integrating (I was trying to integrate but I was just being retarded), and got my answer from there. Will I get a mark?

EDIT: Btw thanks a lot for the solutions!
Is this your actual teacher? Seems a bit weird but I suppose it's a good idea too.
17. for 4b i put e^x2 and not 2x. hw much wud i lose and for the last i intergraded put the the y values. ie e^4 one in but got soma dfferent. like 2pi e^4. i also integrated the line and wrkd that out?
18. (Original post by Junaid96)
Is this your actual teacher? Seems a bit weird but I suppose it's a good idea too.
Maybe

Just kidding, nope but I do casually stalk Mr M (Only on TSR lol) would be so weird if someone did that in real life
19. How many marks would I lose for getting

k = 3/5
c = 40

Because I read the question as 37 not MINUS 37!
20. (Original post by Mr M)
Mr M's OCR (not OCR MEI) Core 3 Answers June 2012

Thanks. Just two questions.

On question 9iii) if I used my answer from question 9ii) to calculate the volume (but followed the correct method) would I get any of the 2 marks?

Also, on question 9ii) I got an incorrect answer as when I substituted in the limits I rewrote ln(e^4) as e^4 instead of 4. However, I applied the limits correctly to the other variables. (And applied the correct method throughout) How many marks out of the 6 is this likely to have costed me?

Thanks a lot

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Updated: August 29, 2012
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