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# C3 (Not MEI) - Thursday June 14 2012, AM

Maths exam discussion - share revision tips in preparation for GCSE, A Level and other maths exams and discuss how they went afterwards.

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1. Re: C3 (Not MEI) - Thursday June 14 2012, AM
how are we supposed to lay out the iterative questions where we have to find the roots?

i know how to do them, just not sure of how to present them
2. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by ugk4life)
how are we supposed to lay out the iterative questions where we have to find the roots?

i know how to do them, just not sure of how to present them
Set them up like this
x0= Starting value
x1= 2nd value
x2= 3rd value

etc....

Until you have two answers the same for the given decimal place(in question), for each iterate you should write about 6 sig figs
3. Re: C3 (Not MEI) - Thursday June 14 2012, AM
CAN SOMEONE PLEASE GIVE ME THE SOLUTION TO 9iii OF JUNE 2010?????
4. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by lamalas600)
You know that it's mass is initially 40 grams, and 2years later 31.4 grams, and it's an exponential.

Therefore you know at time=0 (initially) it's 40 grams therefore M(40)= there x must be equal to 40.

Then you have M=40e^kt (time and k=constant)
Your given 2 years later it's 31.4... 31.4=40e^2k

Can you do the rest?
Thank you so much! I had something like this in mind but was using a less logical value for k. Thanks!
5. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by lamalas600)
Set them up like this
x0= Starting value
x1= 2nd value
x2= 3rd value

etc....

Until you have two answers the same for the given decimal place(in question), for each iterate you should write about 6 sig figs

(Original post by lamalas600)
Set them up like this
x0= Starting value
x1= 2nd value
x2= 3rd value

etc....

Until you have two answers the same for the given decimal place(in question), for each iterate you should write about 6 sig figs
cool thanks.
6. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by 1234girl)
CAN SOMEONE PLEASE GIVE ME THE SOLUTION TO 9iii OF JUNE 2010?????
Put the equations equal to each other and equate coefficients of either b or a i think and rearrange.
7. Re: C3 (Not MEI) - Thursday June 14 2012, AM
Anybody have the Jan 2012 MARKSCHEME ?
Last edited by Master S P; 13-06-2012 at 20:24.
8. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by Master S P)
Anybody have the Jan 2012 MARKSCHEME ?
9. Re: C3 (Not MEI) - Thursday June 14 2012, AM
Can any one explain how to do Q7(ii) part b from the June 2009 paper please?
10. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by kontemptXD)
Can any one explain how to do Q7(ii) part b from the June 2009 paper please?
Relate it to the 8sin(theta)-6cos(theta) and then take values of x and y to plug into the equation given in part (b) i.e. 1 or -1
11. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by 19hannah94)
Relate it to the 8sin(theta)-6cos(theta) and then take values of x and y to plug into the equation given in part (b) i.e. 1 or -1
I took a similar approach and ended up with 40 - 20 but the mark scheme answer is 60. The examiners report on the question hasn't really helped me to comprehend why. Can you explain further?
12. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by kontemptXD)
I took a similar approach and ended up with 40 - 20 but the mark scheme answer is 60. The examiners report on the question hasn't really helped me to comprehend why. Can you explain further?
You should get a double negative 40 - -20 = 60
13. Re: C3 (Not MEI) - Thursday June 14 2012, AM
hey can someone explain june 11 qu 6 please
14. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by ugk4life)
hey can someone explain june 11 qu 6 please
It's a long question... the x=10/3 bit or the find area bit
15. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by lamalas600)
From the first part you know that
Let's do some rearranging..
It is given in the question that
Plug that into
Thanks a bunch.
16. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by lamalas600)
It's a long question... the x=10/3 bit or the find area bit
no worries, seen it explained on an older thread.

the x=10/3 was confusing me though
17. Re: C3 (Not MEI) - Thursday June 14 2012, AM
Hey could someone please explain Jan 2012 question 8iii please? Much appreciated...
18. Re: C3 (Not MEI) - Thursday June 14 2012, AM
Does anyone know what is usually the lowest mark for 90ums+
19. Re: C3 (Not MEI) - Thursday June 14 2012, AM
(Original post by Aimanos)
Hey could someone please explain Jan 2012 question 8iii please? Much appreciated...
I am assuming you have done 8i and 8ii?
You should have 1 - 8sin^2xcos^2x for 8i and (2- route 3)/16 for 8ii.

Cos4x = 2cos^2 2x - 1 = 1 - 8sin^2xcos^2x.
cos4x + 1 = 2cos^2 2x (substitutes for first part)
re arranging some of the equations you can get 8sin^2xcos^2x = 1-cos4x ( /3 then substitute for second part)

So,

8/3 sin^2xcos^2x = (1-cos4x)/3

plug in (1-cos4x) where 2cos^2 2x is and (1-cos4x)/3
where 8/3 sin^2xcos^2x and your equation should look like 1 - cos4x - (1-cos4x)/3

get the same common denominator so you get 3/3 - 3cos4x/3 - (1-cos4x)/3

rearrange to get (4cos4x + 2)/3

max cos4x can ever be is 1 and min cos4x can ever be is -1,

So max and min points are 2 and -2/3.

I have probably made heavy work of this questions but In short, Your substituting cos4x into the equation where you can by rearranging what you did in 8i.

Hope this helps
20. Re: C3 (Not MEI) - Thursday June 14 2012, AM
not confident at all, but only retaking to try gain A*

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Last updated: June 15, 2012
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