OCR MEI AS Mathematics Core 1 13/05/2013

Original post by siriuspudh

Do you reckon I would have lost a mark for putting pos/neg in that rearranging question when r>0?

Unfortunately, I think you will suffer a 1 mark deduction. I think this question caught me out too. None of the past papers have something like "x>0 or t>0" so this caught me out. Oh well. Hopefully, this was the one of the only marks I lost.

Reply 222

krishparscrotam

My answers were as follows:
1. y=-0.5x+3
2.(0.7,0.1)
3.i) 25 ii)8a^9
4. r=squareroot 3V/pi(a+b)
5. k=3
6. -2560x^3
7.i)5^3.5 ii)8+11root5
8. 3(x-2)^2 -7 and minimum y value was -7
9i) 3n ii) 3n^2 + 2 and then i did a bit of waffling
10i). radius= 2root5 and centre (3,2)
ii) y values 2+_root11 and x values were -1 and 7
iii) midpoint AB (4,5) and distance of chord thingy was root10
11i) draw graph
ii) -2,0, 7/2
iii) (2x+9)(x+1)(x-1)
12i) points of intersection were (-1.6,-0.3) and (2.1,7.2)
12 ii)1+_root57/4
iii) 0 = x^2 -2k(x+1) +1 when i equated the two lines and my k value was completly wrong though i did write b^2-4ac=0 in the last part which should give me a mark.
so overall would you say these answers are correct apart from the last part of 12 and 7ii ?

Any help would be appreciated

Reply 223

Original post by krishparscrotam

My answers were as follows:
1. y=-0.5x+3
2.(0.7,0.1)
3.i) 25 ii)8a^9
4. r=squareroot 3V/pi(a+b)
5. k=3
6. -2560x^3
7.i)5^3.5 ii)8+11root5
8. 3(x-2)^2 -7 and minimum y value was -7
9i) 3n ii) 3n^2 + 2 and then i did a bit of waffling
10i). radius= 2root5 and centre (3,2)
ii) y values 2+_root11 and x values were -1 and 7
iii) midpoint AB (4,5) and distance of chord thingy was root10
11i) draw graph
ii) -2,0, 7/2
iii) (2x+9)(x+1)(x-1)
12i) points of intersection were (-1.6,-0.3) and (2.1,7.2)
12 ii)1+_root57/4
iii) 0 = x^2 -2k(x+1) +1 when i equated the two lines and my k value was completly wrong though i did write b^2-4ac=0 in the last part which should give me a mark.
so overall would you say these answers are correct apart from the last part of 12 and 7ii ?

Any help would be appreciated

Hi,

I got the same answers as you except for 7ii and 12iii.

Can you remember the question for 12ii)?

Thank you.

Reply 224

Soho32

Original post by thisisjokes

I did exactly this and for some reason didn't see that 1/0.04=25.
Really hope I don't lose a mark for it

yeah i didnt see that either hopefully its fine

Reply 225

hey guys for question 4 I got:
r = ((3V/(a+b))/pi)^1/2

Is this correct?
original equation was 1/3(r^2)pi(a+b) = V

slowly finding out i got more and more wrong.

(edited 10 years ago)

Reply 226

Dr.Monstaa

Original post by Deceived

Hi,

I got the same answers as you except for 7ii and 12iii.

Can you remember the question for 12ii)?

Thank you.

The question to 12ii) was when you had to equate 1/(x-2) and y=2x+3 to give the quadratic then solve to find points of intersection I think :/

Reply 227

Original post by Dr.Monstaa

The question to 12ii) was when you had to equate 1/(x-2) and y=2x+3 to give the quadratic then solve to find points of intersection I think :/

Oh yeah, I remember now. Thanks.

This is what I got:

2x+3=1/(x-2)

(2x+3)(x-2)=1

2x²+3x-4x-6=1

2x²-x-7=0

x²-(1/2*x)-(7/2)=0

(x-1/4)²-(1/16)-(56/16)=0

(x-1/4)²=57/16

x-1/4=±√57/4

x=1/4±√57/4

x=(1±√57)/4

So yeah, I got a different answer.

Reply 228

you got the same answer.....

Reply 229

Moon1ight

15

I felt so happy after the exam,now I feel very nervous - I hope the grade boundary is like 56 for an A because I'm assured ill at least get a B worse comes to worst - I'm hoping I've got at least 60 out of 72 though - going to have to do 3 core 2 past papers a day if I want to be prepared for Friday

Posted from TSR Mobile

Reply 230

ElChapo

18

Original post by krishparscrotam

My answers were as follows:
1. y=-0.5x+3
2.(0.7,0.1)
3.i) 25 ii)8a^9
4. r=squareroot 3V/pi(a+b)
5. k=3
6. -2560x^3
7.i)5^3.5 ii)8+11root5
8. 3(x-2)^2 -7 and minimum y value was -7
9i) 3n ii) 3n^2 + 2 and then i did a bit of waffling
10i). radius= 2root5 and centre (3,2)
ii) y values 2+_root11 and x values were -1 and 7
iii) midpoint AB (4,5) and distance of chord thingy was root10
11i) draw graph
ii) -2,0, 7/2
iii) (2x+9)(x+1)(x-1)
12i) points of intersection were (-1.6,-0.3) and (2.1,7.2)
12 ii)1+_root57/4
iii) 0 = x^2 -2k(x+1) +1 when i equated the two lines and my k value was completly wrong though i did write b^2-4ac=0 in the last part which should give me a mark.
so overall would you say these answers are correct apart from the last part of 12 and 7ii ?

Any help would be appreciated

Not sure about your answer for question 1 and 7ii is wrong for sure. the last part of question 12 was k= 0 or 4 (unfortunately only put 4) given 2 more minutes i would've got the 0

Reply 231

Original post by TheNote

you got the same answer.....

How did we?

1±√57/4 ≠ (1±√57)/4

Brackets make all the difference.

Reply 232

user1-4

1

Original post by Pjmckenna96

Does anyone know of an unofficial mark scheme available online?

there probably wont be one cos it is mei

Reply 233

Original post by krishkmistry

I felt so happy after the exam,now I feel very nervous - I hope the grade boundary is like 56 for an A because I'm assured ill at least get a B worse comes to worst - I'm hoping I've got at least 60 out of 72 though - going to have to do 3 core 2 past papers a day if I want to be prepared for Friday

Posted from TSR Mobile

Feeling exactly the same. Wish I never came on this forum haha. I know I've dropped at least 1 mark from the ± mistake on the re-arranging question. Other than that I think I'm fine. Hopefully, I didn't make many stupid mistakes in the exam. Good luck with C2. I've done all the past papers and therefore don't have much revision material left haha.

Reply 234

Original post by Deceived

How did we?

1±√57/4 ≠ (1±√57)/4

Brackets make all the difference.

i am assuming he meant brackets due to a typo

Reply 235

user1-4

1

does anybody the last question? We can go through it and figure out the 'actual answer.'
See if it is 4/0 or the other one

Reply 236

Original post by TheNote

i am assuming he meant brackets due to a typo

Thanks for clearing that up.

Reply 237

SFCMorganBT

On the last part of 12 I tried to differentiate the (x-2)^-2 (C3/C2 differentiation), make dy/dx=-1 (because y=-x+k) then tried to find k from that. I ended up with -4/3 and -16/5 or something.. lots of room for error with that so not that confident with those...

Reply 238