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

1. (Original post by Aimee18)
If anybody here did the biology unit 5 paper and thought it was a disgrace like this page please

I didn't think it was so bad? Just a lot of application.
2. Sorry - did someone say that the volume they found for the balloon was 30.5? How does that work given that at t=5, r=9 which gives a volume of around 3000cm^3.
3. average A grade boundary over the past 6 c4 papers is 56.5, my thinking is that this was a lot harder than a normal c4 paper so i'd be very surprised if the A grade boundary was above 55.
4. Can I also just point out, you can plot points of the graph on the Casio calculator. That Wouk have also showed you that te point was a minimum

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5. (Original post by QuestionsQ)
Sorry - did someone say that the volume they found for the balloon was 30.5? How does that work given that at t=5, r=9 which gives a volume of around 3000cm^3.
the r=9 is when t=5, the question was asking for the volume when t=0 and therefore r=1.9....cm.
6. (Original post by QuestionsQ)
Sorry - did someone say that the volume they found for the balloon was 30.5? How does that work given that at t=5, r=9 which gives a volume of around 3000cm^3.
It was at t=0, unfortunately

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7. (Original post by Namige)
For god's sake. Graph sketching is only used for C1, and if you didn't know how a graph of -x^2 looks, then you pretty much are screwed for the rest of the paper. Plus, it is only 1 or 2 marks and to sketch the graph on a graphic calculator would take about 20 seconds for it to draw. You could draw the graph by working it out within 10 seconds.

And the answer it gives for integration questions can be given from a £14 casio calculator. It does it no more accurate, or faster. The only advantage a graphic calculator gives is a larger screen.

Unless you actually own a graphic calculator, please don't complain about it.
You obviously haven't taken an FP2 exam, it goes far beyond a quadratic graph, taking a lot longer than a few seconds to sketch XD... I think even "tooambitious" would agree.

I'm not talking about just graphic's calculators, any calculator which gives you an advantage over function keys (like sin, cos) and calculating values.

You need to read my previous post.
8. (Original post by tooambitious)
Can I also just point out, you can plot points of the graph on the Casio calculator. That Wouk have also showed you that te point was a minimum

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9. (Original post by printergirl)
i like you jakepreedy

tooambitious you're a nice guy

nimage you and your graphic calculator can go back to whatever idiot hellhole you came from
don't make me blush

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10. (Original post by printergirl)
Haha, yeah there is, no worries now anyway

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11. (Original post by ChrissM)
I'd be surprised if you drop more than one mark for that. I think it was only out of 5, so you'll probably just drop a method mark. I wouldn't panic about it!
Wah really? But I integrated tan2x to lnsec2x, not 1/2lnsec2x.

Would I really only lose one mark?
12. (Original post by tooambitious)
Can I just be very clear, for JakePreedy and Printergirl that your argument that use of a graphic calculator is cheating really just does by make sense.

If its unfair, yes, perhaps in exams where you get marks just for the graph (not in C4) but then talk to OCR, don't insult people. It's wholly unnecessary.

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"Don't get me wrong, I know that they are not cheating (that was a slip of the tongue), but I still think you can't defend the fact that it gives you an advantage (how little it may be)."

I am sorry if you feel that I have insulted you, I certainly didn't intend to.
13. Great work Benjy100

(Original post by Benjy100)
This is effectively a preliminary markscheme until Mr M posts his full definitive solutions. Some of my answers may be wrong. Spoilered incase you don't want to see them

*A few additions have been made to the markscheme* - namely the cartesian equation (forgot to put it in)

Spoiler:
Show
1.

2.

3. Skew. Solved the first two equations for and and then substituted into the third equation for 18=-38 which is clearly untrue, thus the equations are inconsistent and the lines are skew.
(Also need to demonstrate that they're not parallel by considering the direction vectors)

4.

Stationary points are

5.

Integral was

6.

7.

Angle BAC = 171.3 degrees (1 d.p.)

Show that AD is perpendicular to AB and AC by finding the dot product of AD and AB, and then AD and AC - and showing that both dot products equate to 0.

Volume = x Area of ABC x AD =

8.

Letting t=0, finding r and substituting gives V = 30.5 cm^3 (3 s.f.)

9.

Solving dy/dx yields t=1 which corresponds to the point (0,3)

When t>1 x<0 and dy/dx is negative
When t<1 x>0 and dy/dx is positive

Hence it is a minimum

Cartesian equation...

10. Show.

Let x=0.1 for 0.136

Same substitution would be unsuitable as the expansion here is valid for which is the same as

Or you could just state that 1/x = 10 which is greater than 1 so it is unsuitable

14. (Original post by printergirl)
i like you jakepreedy

tooambitious you're a nice guy

nimage you and your graphic calculator can go back to whatever idiot hellhole you came from
This post actually made me laugh so much :L
15. (Original post by tooambitious)
It was at t=0, unfortunately

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No, I know - I was just comparing that volume to the volume others got - I got around 6.9cm for my radius - and I have no idea how I did that wrong. This is really bad. Really bad indeed.
16. (Original post by tooambitious)
don't make me blush

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tooambitious, how have you had almost 6,000 posts? :O
17. (Original post by JakePreedy)
You obviously haven't taken an FP2 exam, it goes far beyond a quadratic graph, taking a lot longer than a few seconds to sketch XD... I think even "tooambitious" would agree.

I'm not talking about just graphic's calculators, any calculator which gives you an advantage over function keys (like sin, cos) and calculating values.

You need to read my previous post.
Yeah, I can't draw graphs for sit, definitely lost two marks on the polar for FP2
Realised with a minute to spare, and my axis took up all the space, oh well, just means I have to try for M2

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18. For what it's worth, I think a lot of A level students would find this a tough paper; I'd expect the grade boundaries to be lower than average.
19. (Original post by printergirl)
i like you jakepreedy

tooambitious you're a nice guy

nimage you and your graphic calculator can go back to whatever idiot hellhole you came from
Back at ya ;-)
20. (Original post by XingBairong)
This post actually made me laugh so much :L
why dont you show me some gratitude with a little thumbs up

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