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

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Maximum of 40 marks... woo...

Couldnt find N. Made a quadratic that didnt work but then managed to fumble the right answer using trial and error. N was 24 for anyone wondering

Reply 142

ben5312

What did a = for the coefficient q

Reply 143

Mr_hawaii

It was a really weird exam, they pulled questions that Hadn't been used in the whole spec

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Reply 144

xsanda

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

(edited 8 years ago)

Reply 145

Nathanburns01

Original post by ben5312

What did a = for the coefficient q

2/3

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Reply 146

Mr_hawaii

In the time it'd been running

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Reply 147

AlistairMcDonald

Original post by xsanda

Xsanda's solutions:
R=-2
ar¹⁰ = 3072
Sum to 20 = -1048575

trapezium: 21.4
narrower strips

triangle area: 32.1
perimeter: 20.7

expansion: 64+192ax+240a²x²+…
a=2/3

y=4x^(3/2)-7x-3
(x-2)(x+5)(x-3)
256
negative section of integration counts negatively

u₂₀ = 62
Σ = 517 (show that)

N=24
n=17.1
x=32, y=8

6π-α
3π-a
graph of sin, half height
3.32, 12.7

Speedy x_x

Reply 148

Mr_hawaii

That has just given me so much confidence! Thanks xandra

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Reply 149

minimist

Very last part of the last section I messed up straight away by dviding 2cos1/3x by cos1/3x.. Carried on though to get two solutions correct to what I was doing.... Any marks at all? How marks was it worth?

Reply 150

AlistairMcDonald

Original post by xsanda

I've gotta know... How the heck do you remember all of those answers?!

Reply 151

ZAK5YAK

Original post by xsanda

For the sum to 20 one did you but the negative number in brackets? I got the same as you but put it in brackets and got a more sensible andwer if i remember correctly!

Reply 152

fayecaravelli

Original post by xsanda

For the expansion I put 240(ax)^2, will I lose a mark for this because it said to simplify so I didn't know if I had to expand out the brackets fml

Reply 153

eddy29

Original post by xsanda

May just be me, but 12.7 isn't in the range of 0 to 2pi

Reply 154

xsanda

Original post by eddy29

May just be me, but 12.7 isn't in the range of 0 to 2pi

The range is 0 — 6π, because it was sin(1/3 x) so the range had to be tripled.

Reply 155

AlistairMcDonald

Original post by Zallin98

For the sum to 20 one did you but the negative number in brackets? I got the same as you but put it in brackets and got a more sensible andwer if i remember correctly!