OCR (not OCR MEI) Core 3 answers Jan 2011

thanks, is an A* feasible then??
really need it fr the cambridge offer :P

please help ....

how many marks for differentiating on 9 ii)...

thanks for all the help mr M

for Q4 I put 25sin(theta + 73.8) instead of + 16.8 i did 24/7 instead of 7/24

I then worked out the answer for the next part using this answer.

assuming I did part ii correct using 25sin(theta+73.8) how many marks would I lose for Q4

OCR (not OCR MEI) CORE 3 answers Jan 2011


1. $x=\frac{a}{3}$ or $x=-3a$ (3 marks)


2. Translation 3 units in negative x direction, reflection in x axis, stretch scale factor 4 in y direction. Stationary points (-5, 24) and (-3, 0) (4 marks)


3. $\frac{dA}{dt}=45000 \, cm^2 hr^{-1}$ (3 marks)


4. (i) $25\sin(\theta + 16.3)$ (3 marks)

ii) $\theta = 12.4^\circ$ or $\theta = 135^\circ$ (4 marks)


5. $V=24 \pi \ln 5$ (9 marks)


6. i) $\frac{dy}{dx}=\frac{-2(3x^3-16x-3)}{(x^3-4x^2+2)^2}$ and show ... (4 marks)

ii) (2.398, -1.552) (5 marks)


7. i) $x=\sqrt{e^8 - 8}$ (3 marks)

ii) f has inverse $f^{-1} (x) = e^x$ (3 marks)

iii) $\frac{6}{e^3}$ (3 marks)

iv) 20.3 (3 marks)


8. a) i) 2 positive U shapes and 2 negative inverted U shapes (3 marks)

ii) $\beta = 3\pi - \alpha$ (2 marks)

b) i) (1 mark)

ii) $\frac{225}{322}$ (6 marks)


9. i) a) Show ... (3 marks)

b) Show and (5 marks)

ii) $y \geq 2 \sqrt k$ (5 marks)

Hey mr m, thanks for all of the help! How many marks for differentiating 9 iii and stating the SP = 0, then making a very limited attempt to solve it for x?

How many marks would I lose on 1st question, if I wrote both the answers but a=, instead of x=?

Thanks for the answers mr m
For question 1 did you need to get more than 1 answer?
And for q2 i struggled in drawing the graph but listed the transformations and stated the stationary points, do u think il gain any marks for doing this?
And finally i made a really silly mistake on question 5 and got a wrong value of a, all the rest of my working was correct, how many marks do u think il lose?
thanks so much for all of the help its much appreciated

hi mr m - thanks for posting the answers up i got a few questions:

2) i think i drew the correct grah and labelled the correct stationary points. i also stated the translation and stretch of sf but this case (-4), therefore i forgot to mention reflection: how many marks will i lose?

5) I can't remember what i got here but i think i wrote 12 something...will you be able to go through the method of that question with me.

6ii) for this question i got (2.399,-1.522), therefore are you sure the answer is right. if your answer is right, how many marks will i lost considering i did the iterative process correct?

8aii) here, i put -cosec(x-2pi) will i get any marks?

8bii) for this question, i figured that tanx=1/4 and then i multiplied out tan4x=tan(2x+2x) and changed cotx to 1/tanx etc...but my answer was 100/161 how many marks will i lose?

9ia) for this question i diffrentiated then put in values of x=1, x=-1 and x=0 to come to a answer than the derivative is greater than 0, therefore how many marks will i lose

bi) could you go over this question with me because i didn't get the right answer but how many marks will i lose if i diffrentiated again to find the second derivative?

9ii) i didn't have enough time to finish but stated that the answer can be found if k was found and one that equation was differentiated, then it can be equated to 0 to find the stationary point hence the range? will i get any marks for that question.

thanks again for taking time in reading my message and as a whole - how hard do you think this paper was compared to all the other past papers? what mark boundary will you reckon for a C, B and A?

I've done so badly... I worked out my maximum mark is 43/72 and thats with a hell of a lot of luck. I didn't even write anything for 4 ii) or iii) and nearly nothing for all of 8 or 9...

Anyone starting revision for June resits yet?