OCR (Not MEI) Core 3 - Post Exam Discussion

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It went pretty well until 8(iii) and 9(iii). Did people get 52/9 pi for volumes of revolution question and something like 27x + 3y - 32 = 0 for equation deducing question?

Yes, something like that. 8 iii) was a difficult question, although I think with more time I could've at least had a crack at it.

I thought 9 was a decent question (that's if I did it right), I really dislike thinking about what I could've done wrong though.

Reply 21

harry3

did anybody actually get answers for the last two questions? 8 and 9?

Reply 22

RooT_Fifteen

Original post by PhysicsMan

If one thing is for sure, I found it way harder than all of the other C3 past papers- I was getting usually 85-95% on them! Don't think I will on this, unless the grade boundaries are low- which they actually might be.

Until Q7 it was just a normal difficulty C3 paper. But Q8 and 9 were not nice indeed. I would guess UMS drop of about 6 - 7 marks though

subscibed

for question 9) iii

I got k=5

solutions when |f(x)|=20

is when:
x= -2
x= (-2+root2)
x= (-2-root2)

*edited- they were not /2 , jsut got carried away with my 2's :biggrin:

(edited 12 years ago)

Reply 25

RooT_Fifteen

Original post by harry3

did anybody actually get answers for the last two questions? 8 and 9?

for 8iii i got maximum of 2/3 minimum of -2 (it could have been 2 and -2/3 but i cant remember exactly. I proved the trig though so Im presuming i put down the right one)

For 9 it was translate in x by -2, translate in y by -4 and stretch by k

and the roots of modulus question was -2, -2-2root2, -2+2root2

^ or something similar. My discriminent was root32

Reply 26

PhysicsMan

Original post by RooT_Fifteen

Until Q7 it was just a normal difficulty C3 paper. But Q8 and 9 were not nice indeed. I would guess UMS drop of about 6 - 7 marks though

Yeah, I suppose you're right. Q8 and 9 were, in my opinion, highly unusual C3 questions- I'd never really see much like them before.

But, for Q9 (i) I got translate by -2 x-direction, -4-y direction and stretch scale factor k in y direction, and (ii) I got f(x) >= -4k. Not much of a clue for (iii) though!

Reply 27

ms12

Original post by RooT_Fifteen

for 8iii i got max 2 and minimum of -2/3. I got the same answers for all of 9 tho.

Reply 28

BLAseeK

Original post by RooT_Fifteen

I can confirm the 8iii) question to be max of 2 and min of -2/3

although someone I know used their graphics calculator which gave them a smallest value of negative 6, which is incorrect which is good news as just because he has a £100 calculator he can still misstype numbers

Reply 29

PhysicsMan

Oh damn, I was going to put -2+root(2) and vice versa but it didn't work in the modulus equation to get 20 when I checked it!

Reply 30

Stainton93

What did anyone get for k in question 8 i)?

Reply 31

Femto

Original post by BLAseeK

I used my graphical after I'd done it and it's definitely 2 and -2/3

Reply 32

PhysicsMan

Original post by Stainton93

What did anyone get for k in question 8 i)?

I got k = 8

Reply 33

Thebestgod

Original post by RooT_Fifteen

Did you get the range of f(x) to be k>=-4?

Reply 34

Just Josh

Ah phew, i started reading this then my heart panicked, then realised this is Not Mei :tongue:

*sigh of relief*

Reply 35

BLAseeK

Original post by Thebestgod

Did you get the range of f(x) to be k>=-4?

range was

F(x)>-4k

it wanted the range of the function it terms of k
not the range of k

Reply 36

RooT_Fifteen

Original post by Femto

I used my graphical after I'd done it and it's definitely 2 and -2/3

It was one or the other. I just cant remember my values very well ¬_¬

Reply 37

DanielReece

Original post by RooT_Fifteen

For 9 it was translate in x by -2, translate in y by -4 and stretch by k

and the roots of modulus question was -2, -2-2root2, -2+2root2

^ or something similar. My discriminent was root32

That seems about right, I think I left mine in terms of root8 though, don't really care if I drop a mark for that but I don't specifically recall them asking for a simplified root.
Thank god someone agrees with my answer though, I was thinking I'd done it wrong as it seemed a little too easy.