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

1. (Original post by AlfieH)
Can someone please explain the summation = 517 I suck at those haha!

You had do what ever the top value was sum - the bottom n -1 sum

(And then use this idea to do the quadratic for the 6marker in the next part)
2. (Original post by Zallin98)
Thats what i got i think!
Unfortunately we're wrong The power was supposed to be n (20) not n-1.
3. (Original post by ella_chloe)
7/8
5, maybe a 6...
4. How did everyone prove that the answer was 517 for one of the summations question?
5. Had problems with the sum to 2750 question, kept on mucking up the quadratic so in the end i got 23.9, how many marks do you think i will drop?
6. (Original post by eyenarbi)
I also got that but idk what is the gradient of 5 for?
You must integrate twice and to first integration gives dy/dx and hence this gradient allows you to find out the first c (the -7)
7. (Original post by DominoMatrix227)
How did everyone prove that the answer was 517 for one of the summations question?
The question was the sum from 10 to 20 of Un i think. You had to do the sum of 1 to 20 and then take away the sum of 1 to 9. As a result you got 670 - 153 i think
8. (Original post by AlfieH)
Can someone please explain the summation = 517 I suck at those haha!
I worked out the sum of the first 9 terms and then the sum of the first 20 terms using the formula book and subtracted them from each other since it asked for the sum between 10-20
9. (Original post by AlfieH)
Think you could be my C2 Doppelgänger?
Lol, I hope you weren't 3 minutes late to the exam
10. (Original post by eyenarbi)
I also got that but idk what is the gradient of 5 for?
When you integrate d2y/dx2, to find c, I think
11. (Original post by ella_chloe)
laugh at what sorry?
I think 60 is a little high for that paper, there was a lot of random jazz on it. I found it ok, but everyone I spoke to found it pretty hard going
12. (Original post by Brian luiz)
Had problems with the sum to 2750 question, kept on mucking up the quadratic so in the end i got 23.9, how many marks do you think i will drop?
Hi would you remind me of the initial quadratic? It was 5N2 + 5N -55000 = 0? or was it
13. (Original post by AlfieH)
Can someone please explain the summation = 517 I suck at those haha!
Sum from 10 to 20
= Sum from 1 to 20 - Sum from 1 to 9

20/2 (2a+19d) - 9/2 (2a+8d)
= 517
14. (Original post by Nuvertion)
Unfortunately we're wrong The power was supposed to be n (20) not n-1.
i dont know what i put honestly! I got both answers but cant remember what i put as my final one!
15. Can someone remind me of the amount of marks per question so i can tally up an approximation of what I got?
16. (Original post by Mr_hawaii)
I think 60 is a little high for that paper, there was a lot of random jazz on it. I found it ok, but everyone I spoke to found it pretty hard going
oh i my question was if i get 60/72 would i get an A i wasnt predicting the boundary!
17. (Original post by doommiinniikky)
The question was the sum from 10 to 20 of Un i think. You had to do the sum of 1 to 20 and then take away the sum of 1 to 9. As a result you got 670 - 153 i think
Well I got 670 but got 150 for the next bit, subtracted this then subtracted 3 (I stated a=3). Wondering how many marks I'll get
18. Was the 2750 question and ap or gp?

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19. (Original post by RIPJakeSpliff)
how do dis I no no it how u no get it. peasy paper u scrubs even I (an art student) got it.
RIPjakespliff u sound like u no ur stuff
20. (Original post by TCO)
Was the 2750 question and ap or gp?

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Arithmetic

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