OCR (not MEI) C2 - Wednesday 20th May 2015

Original post by TCO

Thanks I think I messed up my arithmetic got N to be 125/3 arghh

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i got exactly the same!! what have we done wrong??

Reply 401

Dom1997

Original post by Jmedi

If you calculate it you get 256 and this is incorrect as it should be higher than this;
some area gets subtracted as a small part of the area is below the x axis

I got 256 as did my Teacher and most of my class I'm sure it's right?????

Reply 402

Original post by DominoMatrix227

What did you get for the 2N thing? I got -44 and 125/3 which I think are both wrong.

Didn't you do any of 9?

i got that and everyone seems convinced it is not the case, I'm not sure why!

Reply 403

Jmedi

Original post by Dom1997

I got 256 as did my Teacher and most of my class I'm sure it's right?????

256 is the correct answer for the integral however this is not the true area of the x axis to the graph line as it goes below the x axis. (Hence this was the following part of the question.
(The true area was around ~258 )

Reply 404

Jmedi

Calculation of N ; C2 2015 q.pdf

Original post by clarafitzgerald

i got exactly the same!! what have we done wrong??

Reply 405

Parallex

Original post by clarafitzgerald

i got that and everyone seems convinced it is not the case, I'm not sure why!

What's the 125/3 term of a sequence?

That's why it's wrong.

Reply 406

EconEast

Original post by Orangeflower360

TBH i got the 3.3 wth didnt i add the 180 degrees my dayss idiot right here :' :wink:

thank you for taking the time!

no problem

Reply 407

Original post by Parallex

What's the 125/3 term of a sequence?

That's why it's wrong.

No need to be so pretentious :smile:

Reply 408

Calculation of N ; C2 2015 q.pdf

Original post by Jmedi

really don't understand why that method is used

Reply 409

xsanda

If anyone is looking for an unofficial markscheme, I'll post it again:

Xsanda's solutions:
1i) common ratio:[1]
r=-2
1ii) 11th term: [2]
ar¹⁰ = 3072
1iii) sum to 20: [2]
Sum to 20 = -1048575

2i) trapezium rule: [4]
21.4
2ii) improvement: [1]
more/narrower strips

3i) shaded area: [4]
32.1
3ii) perimeter: [5]
22.7

4i) Binomial expansion: [4]
64+192ax+240a²x²+…
4ii) Find a: [5]
a=2/3

5) Double antidifferential: [7]
y=4x^(3/2)-7x-3

6i) Factorise: [4]
(x-2)(x+5)(x-3)
6ii) Integrate: [4]
256
6iii) Problem with integral: [2]
negative section of integration counts negatively

7i) u₂₀: [2]
62
7ii) Σ 10 to 20 show that: [3]
517
7iii) Σ N to 2N: [6]
N=24

8a) log 2^(n-3) = 18000: [4]
n=17.1
8b) simultaneous logs: [5]
x=32, y=8

9ia) Next solution of cos: [1]
6π-α
9ib) Solution with negative: [2]
3π-a
9ii) Draw graph: [2]
graph of sin, half height
9iii) Solve graphs: [4]
3.32, 12.7

Reply 410

Rubberduckiller

Original post by DominoMatrix227

I have already asked this, I have no idea! How did you fin d the rest of the paper?

**** hard

Reply 411

Jezzer08

did any one else get the trapezium rule question as 24.8???

Reply 412

JonoTaylor

Original post by xsanda

If anyone is looking for an unofficial markscheme, I'll post it again:

Xsanda's solutions:
1i) common ratio:[1]
r=-2
1ii) 11th term: [2]
ar¹⁰ = 3072
1iii) sum to 20: [2]
Sum to 20 = -1048575

2i) trapezium rule: [4]
21.4
2ii) improvement: [1]
more/narrower strips

3i) shaded area: [4]
32.1
3ii) perimeter: [5]
22.7

4i) Binomial expansion: [4]
64+192ax+240a²x²+…
4ii) Find a: [5]
a=2/3

5) Double antidifferential: [7]
y=4x^(3/2)-7x-3

6i) Factorise: [4]
(x-2)(x+5)(x-3)
6ii) Integrate: [4]
256
6iii) Problem with integral: [2]
negative section of integration counts negatively

7i) u₂₀: [2]
62
7ii) Σ 10 to 20 show that: [3]
517
7iii) Σ N to 2N: [6]
N=24

8a) log 2^(n-3) = 18000: [4]
n=17.1
8b) simultaneous logs: [5]
x=32, y=8

9ia) Next solution of cos: [1]
6π-α
9ib) Solution with negative: [2]
3π-a
9ii) Draw graph: [2]
graph of sin, half height
9iii) Solve graphs: [4]
3.32, 12.7

How sure are you that these are right? I pretty much got the EXACT answers here! Did a teacher work them out?

Reply 413

xsanda

Original post by JonoTaylor

How sure are you that these are right? I pretty much got the EXACT answers here! Did a teacher work them out?

I've checked these with several other people who did the test, and so I'm fairly sure they're right.

Reply 414

Peppercrunch

14

Original post by DominoMatrix227

What did you get for the 2N thing? I got -44 and 125/3 which I think are both wrong.

Didn't you do any of 9?

I got N as 24.random numbers and the answer was exactly 24, so hopefully I got a lot of method marks for it.

I drew the graph.

Reply 415

mikaela_pascal

3

Original post by Jezzer08

did any one else get the trapezium rule question as 24.8???

I did!

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Reply 416

AidenPearce

OKAy. It was a decent paper. Not too hard to get an A and not too easy to get a D/ high C. I reckon I got around 53/54 out of 72 which is okay. One problem that I had is that through core 3 my teacher made a big deal about not dividing cos(x), sin(x) and tan(x) as to not lose any solutions so when I got to that question, the internalized fuss that he made kicked in so I subtfracted stuff and factorised stuff and ultimately mesed up those 4 marks. Can someone explain some cases where you can didvide those trigonometric functions so that I wont make the same. Istake in core 3

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Reply 417

Weeksy97

Original post by xsanda

If anyone is looking for an unofficial markscheme, I'll post it again:

Xsanda's solutions:
1i) common ratio:[1]
r=-2
1ii) 11th term: [2]
ar¹⁰ = 3072
1iii) sum to 20: [2]
Sum to 20 = -1048575

2i) trapezium rule: [4]
21.4
2ii) improvement: [1]
more/narrower strips

3i) shaded area: [4]
32.1
3ii) perimeter: [5]
22.7

4i) Binomial expansion: [4]
64+192ax+240a²x²+…
4ii) Find a: [5]
a=2/3

5) Double antidifferential: [7]
y=4x^(3/2)-7x-3

6i) Factorise: [4]
(x-2)(x+5)(x-3)
6ii) Integrate: [4]
256
6iii) Problem with integral: [2]
negative section of integration counts negatively

7i) u₂₀: [2]
62
7ii) Σ 10 to 20 show that: [3]
517
7iii) Σ N to 2N: [6]
N=24

8a) log 2^(n-3) = 18000: [4]
n=17.1
8b) simultaneous logs: [5]
x=32, y=8

9ia) Next solution of cos: [1]
6π-α
9ib) Solution with negative: [2]
3π-a
9ii) Draw graph: [2]
graph of sin, half height
9iii) Solve graphs: [4]
3.32, 12.7

for the binomial question could you simplify it by dividing all the values by 8??

Reply 418

sandpitturtle

Is mr m posting mark scheme for c2?

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Reply 419

Lil_timmi