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# CCEA A2 maths - C3 20th may 2016 Watch

1. (Original post by Golden hawk)
Well after looking at this again, I know I've done badly now. What was the boundary for an A* last year? Whats the lowest its ever been for an A* as well. This paper was definitely harder than any other c3 paper I've ever done
I don't think anyone will be able to tell you, but I'm sure it will be lower than it has ever been purely because not many PP compare to it. All I know was that summer 2014 pp was a 1:1 ratio from % to UMS if that makes since. So 60/75 was an A etc

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2. [QUOTE=TomFitness;65002765]I don't think anyone will be able to tell you, but I'm sure it will be lower than it has ever been purely because not many PP compare to it. All I know was that summer 2014 pp was a 1:1 ratio from % to UMS if that makes since. So 60/75 was an A etc

I know in summer 2014 an A* was 70/75 and in summer 2013 it was 68/75 for an A*. If it's the summer 2014 grade boundary this year I'm screwed. I just hope it's below 67 or below for the A* otherwise i not get into uni
3. (Original post by Golden hawk)
Well after looking at this again, I know I've done badly now. What was the boundary for an A* last year? Whats the lowest its ever been for an A* as well. This paper was definitely harder than any other c3 paper I've ever done
just emailed CCEA there now to find out the mark boundaries in terms of raw marks for the last 3 years under the FOI, so here's hoping they reply soon
4. (Original post by Mr.bob)
just emailed CCEA there now to find out the mark boundaries in terms of raw marks for the last 3 years under the FOI, so here's hoping they reply soon
What email did you use?
5. (Original post by harrytqo)
and did your newton rhapson method work? mine didnt
The problem here was what you let f(X) to be. You should have had the equation for the differential and not the initial equations so it is actually f'(X)/f''(X) which is quite sneaky. Once you did this it worked fine
6. (Original post by harrytqo)
and did your newton rhapson method work? mine didnt
You had to use as and then differentiate THAT and use it in your NR formula
7. (Original post by harrytqo)
same^ ln0.5/-0.0004 = 1730 years
That's actually not correct. The correct answer is 1700 not 1730 because k is not 0.04.
You go like this
96=100e^-100k
Ln(96/100) = -100k
K = something near 0.04 but not exactly.
Then use that value of k to find t when
1/2=e^-kt
Ln(1/2)/-k = t
T= 1697.???
=1700(3sf)
8. (Original post by hampshir3)
exactly this, no way i would have thought of a method to complete it without doing a whole other subject, ccea get your finger out
I don't do physics and I thought it was OK after a little guessing and knowing that they were trying to poke at an exponential question.
9. I hear people completed the square in q7 but I just differentiated, set that =0 for max/min. Then showed that the minimum occured at X=1/2 and then found the minimum value to be a positive number. Do you think this will be accepted?
10. (Original post by Camderman106)
That's actually not correct. The correct answer is 1700 not 1730 because k is not 0.04.
You go like this
96=100e^-100k
Ln(96/100) = -100k
K = something near 0.04 but not exactly.
Then use that value of k to find t when
1/2=e^-kt
Ln(1/2)/-k = t
T= 1697.???
=1700(3sf)
I've never seen this method before?
11. (Original post by Camderman106)
I hear people completed the square in q7 but I just differentiated, set that =0 for max/min. Then showed that the minimum occured at X=1/2 and then found the minimum value to be a positive number. Do you think this will be accepted?
Yeah, thats a valid method. You could have also sketched the graph, or used the discriminant/ solved it to show there were no real roots etc. There were a few different methods and I'm sure they will all be accepted.
12. (Original post by Smcdonald98)
What did you guys do for 7 part ii? I differentiated it twice to see if d2y/dx2 was greater than 0 but not sure if thats correct
This one was good. When you differentiate I believe the answer was
dy/dx = 2e^(-2x) X (x-(x^2+2))
The value of 2e(-2x) can never be negative, so all you have to do is prove that (x-(x^2+2)) is always negative. But this multiples out to be
-x^2+x-2<0
Which can be rewritten as
0<x^2+x+2
Which was proven in part 1. Therefore it is always negative because a positive X a negative is always a negative which is your proof
13. (Original post by Foutre en L'air)
Yeah, thats a valid method. You could have also sketched the graph, or used the discriminant/ solved it to show there were no real roots etc. There were a few different methods and I'm sure they will all be accepted.
Great, my method for these questions was slightly umconventional but still technically valid so I'm hoping I get credit haha
14. (Original post by Foutre en L'air)
I've never seen this method before?
It's the same method used in every single past paper. The equation for exponential decay is
VALUE=INITIALVALUEe^-kt
V=IVe^-kt
That's the only way I knew the equation is from past paper questions. But you have to figure out k before you can answer it
15. (Original post by Camderman106)
It's the same method used in every single past paper. The equation for exponential decay is
VALUE=INITIALVALUEe^-kt
V=IVe^-kt
That's the only way I knew the equation is from past paper questions. But you have to figure out k before you can answer it
I knew the whole thing, but I've never had to find k before, so I just set it as the rate at which the mass was lost..
16. (Original post by Foutre en L'air)
I knew the whole thing, but I've never had to find k before, so I just set it as the rate at which the mass was lost..
Yeah it's kind of a wee trick. It's just because k is not that simple. You do have to calculate k unless it's given. I know a lot of people who did the same thing as you so do t worry you'll still get most of the marks
17. (Original post by Camderman106)
Yeah it's kind of a wee trick. It's just because k is not that simple. You do have to calculate k unless it's given. I know a lot of people who did the same thing as you so do t worry you'll still get most of the marks
I've never seen finding k like that in past papers or anything, it's not even in the textbook
18. (Original post by Foutre en L'air)
I've never seen finding k like that in past papers or anything, it's not even in the textbook
Yeah its a question about applying your understanding and unfortunately its very very sneaky. I only knew that I needed to calculate k because of physics. Many of the questions in this paper were like that though. Q7 had never come up like that before and Q8 combined about 4 different facts into 1 question. It was undoubtedly a hard paper
19. Can anyone remember what they got for 8a ii, i couldn't get mine to simplify nicely
20. (Original post by Smcdonald98)
Can anyone remember what they got for 8a ii, i couldn't get mine to simplify nicely
Mine didn't either, it was really messy.
I think that I got...
(-2(cosecx)^2.cotx.tan(3x)-3(secx)^2.(cosec)^2)/(tan3x)^2

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