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

Reply 180

would 63 be 90UMS?

OP

Original post by extons

I appreciate you're really busy so thanks for any input you do put in. I just have a few queries re. today's paper.

On the tan(theta-45) or something, I did the whole question until I got to:
(tan(theta) -1) / (tan(theta+1)
Stupidly not realizing we knew the value of tan(theta). Would that get 1/2 of the marks?

Also on the inequality involving the R formula, I got up to the stage of
00>5k+c>00 (forgot numbers)
00>-5k+c>00 and mentioned max when 5sin(theta+59.1) was 5 and min when -5. Divided everything through by 5 and -5 respectively and didn't do any more. What would you guess that would be worth? Obviously it's hard to say without seeing but would you think some credit would be given?

For the last question - like an idiot I integrated and found the volume around the X axis. Completely stupid mistake but I found the volume under the curve, found the volume of the cylinder (about the x axis) and took the volume under the curve from that. Surely some credit must be given to the method or something?!

Thanks!

Just drop 1 mark on the tan question

Understanding the relevance of 5 is worth 1 mark

I'd be incredibly impressed if you actually did find the volume about the x axis as it would require knowledge of the imaginary error function! You might get one mark for subtraction but I can't see you would get anything else.

OP

Original post by Super Mario 64

If you've gotten the correct answer but probably haven't shown all possible working, would you still gain full marks?

probably unless it was a SHOW question

Reply 183

Parkway Drive

9

Hi Mr M, thank you for the answers.

For 3)ii)a) I wrote down the formula but then calculated it wrong. Will I get at least 1 mark?

Also for 8)ii)a) I only got the -64.7. Will I get at least 2 marks on that one?

Also on 6)ii) I put -0.183 instead of 0.183. I forgot that the question said "decreasing." Will that lose me a mark?

Thank you.

OP

Original post by Aadil

If I accidentally got the lower limitwrong but the rest using the method and stuff was.correct how many marks will I get

4?

OP

Original post by Parkway Drive

Hi Mr M, thank you for the answers.

For 3)ii)a) I wrote down the formula but then calculated it wrong. Will I get at least 1 mark?

Also for 8)ii)a) I only got the -64.7. Will I get at least 2 marks on that one?

Also on 6)ii) I put -0.183 instead of 0.183. I forgot that the question said "decreasing." Will that lose me a mark?

Thank you.

3iia) 1 mark

8iia) drop 1 mark

6ii) that's fine - it doesn't matter

Reply 186

FK_

Mr M,

for the last question 9iii), do you know whether the answer had to be exact or could it have been to 3 decimal places?

Thanks

Reply 187

jamieward

70/72 RAW MARKS, if that is not 95 UMS, i will be pisseddddddddddddddd

**** YOU 9 (II)!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Reply 188

Aadil

Just be my error but sin-1 (-1/5) is -11.536. Then I subtracted 53.1 and got -64.636 so isn't that -64.6 to 3.s.f . Mr M did I need to have a more accurate value for 53.1.

Reply 189

samjj8

1

Mr M, could you estimate the grade boundaries please: Someone said between 54 and 56? Could it be more, less?

Sorry if you have already been asked :')

OP

Original post by FK_

Mr M,

for the last question 9iii), do you know whether the answer had to be exact or could it have been to 3 decimal places?

Thanks

No it didn't say exact answer.

Reply 191

Soggy Cherry

Original post by c_subs

Apologies itf this question has been asked already. So please direct me to the link if it has.

Question 9.
I thought that the question was asking you to intergrate a volume of revolution about the y-axis, doesn't this mean to intergrate where you eqaul the equation y=(e^{x^2})/2 to x, so x^2 = ln(2y),
and intergrate ln(2y) to get the volume of revolution.

But you cannot intergrate ln. Or is the paper different, because i'm sure the question was asking us to intergrate and not differenciate.

Appreciate if you can help
Thanks
-->FYI: i forgot the ln in the actualy paper so i ended up intergrating 2y, therefore i didn't notic till exam was over. and Hence did not get the answer ~ nor do i understand how to get to the answer.

Dunno if you've already had a reply, but the integral of ln(2y) was already given in the first part of the question because you had to differentiate yln(2y)-y to show that it equalled ln(2y)

Reply 192

Super Mario 64

3

Sorry for writing in bold but only few more questions and I'll go away. Did 9ii) have to be in a certain form or could you leave the brackets expanded? and what do you think the grade boundaries will be like? Jan 12 was 54 for A and 61 for A*. How hard was this compared to Jan? Thanks!

Reply 193

Soggy Cherry

Hey Mr. M, sorry to be a pain if this question has already been asked.

For the question finding Rsin(theta + angle) I got the wrong angle because I had the fraction upside down when I inversed tan it, and then obviously I carried through this angle in the final part of the question.

Any idea whether that will be okay or will I lose **** loads of marks?

OP

Original post by Super Mario 64

Sorry for writing in bold but only few more questions and I'll go away. Did 9ii) have to be in a certain form or could you leave the brackets expanded? and what do you think the grade boundaries will be like? Jan 12 was 54 for A and 61 for A*. How hard was this compared to Jan? Thanks!

It didn't have to be in a certain form so long as it was an exact form.

I don't guess grade boundaries - just wait and see.

Reply 195

Bless3d

Original post by Mr M

.

Original post by Bless3d

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?

reposting since you might have missed it, thanks.

Just to clarify, the only mistake was subbing in an incorrect lower limit, and thus my final answer, while still in the correct form, included ln 2 - 1, rather than -1/2.

(edited 11 years ago)

Reply 196

Aadil

Original post by Aadil

Just be my error but sin-1 (-1/5) is -11.536. Then I subtracted 53.1 and got -64.636 so isn't that -64.6 to 3.s.f . Mr M did I need to have a more accurate value for 53.1.

Sorry if I didn't make this clear Mr M. But would I still get the marks despite thus

Reply 197

Mattywooda

Hey, Mr M, thank so much!

I thought for question 8 I got k as 0<k<=8 and c=3, as any positive value of k below or equal to 8 satisfies the equations. (5k+c, and -5k+c, between -37 and 42). Or am I wrong?

If I forgot to expand 4b) would I get a least one mark, or none for my incompetence?

Also for your entertainment, i accidentally for 9iii got 4x^2, not 4x (cause I rushed a little :L), and so got a volume ~9000 =D Oopsie!

Cheers

(edited 11 years ago)

OP

Original post by Soggy Cherry

Hey Mr. M, sorry to be a pain if this question has already been asked.

For the question finding Rsin(theta + angle) I got the wrong angle because I had the fraction upside down when I inversed tan it, and then obviously I carried through this angle in the final part of the question.

Any idea whether that will be okay or will I lose **** loads of marks?