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Getting to Cambridge: STEP by STEP!

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Original post by Infinity999
Oh... my bad. I think I get it now. :s-smilie:


You sure?
Original post by Infinity999
Oh... my bad. I think I get it now. :s-smilie:


Also, this is Zain's thread, so I think you should be asking him and not me. You just replied with a thanks for one of his replies. :redface:
Original post by Marxist
Also, this is Zain's thread, so I think you should be asking him and not me. You just replied with a thanks for one of his replies. :redface:


Sorry, I understood your steps better. :tongue:
Original post by Infinity999
Sorry, I understood your steps better. :tongue:


Okay, but it's a bit rude to ask the OP and barely give him a reply. I'm busy, so I cannot help you any further. :blushing:
Original post by Infinity999
Right, that makes sense now. I got the same result as @Zacken did for the derivative. And would I need to do the second derivative to show that it is a maximum?


Or, if I may, you can notice that P is positive, and that it is zero at R = 0 and as R tends to infinity.
Original post by Zacken
He's replied to my comment. :lol:


Can you tell me how please, I'll correct it if I need to.. LMAO
Reply 1186
Avatar for Zacken
Zacken
OP
22
STEP II, 2005:

Total time: 2:50.
Total mark: 109.

Q1: Started with this. Decent question, I ended up playing it safe and went with a quintic instead of a quartic that lead to more effort but was just as valid. 20/20 and 18 minutes.

Q3: Moved on to this one because I knew that it was a straightforward mindless IBP plow that required zero insight and just algebraic manipulation, my judgement ended up being correct. Made an algebraic slip with a factor of a 12\frac{1}{2} and spent a good bit of time looking checking that out. Cute inequality at the end. 20/20 and 20 minutes.

Q4: Bog standard question. I overcomplicate the middle part hugely and got lost in a swath of algebra that I only just managed to escape unscathed. The final bit proved tricky and really worked my arithmetic. Otherwise s'all good. 20/20 and 17 minutes.

Q8: Fairly standard, I feel like I had a more elegant approach to the integration that the official solutions (you lot aren't going to be surprised), but It was easier to note that:

Unparseable latex formula:

\begin{equation*}\frac{x^3}{(x^2 +1)^{5/2}} = \frac{x^3 + x - x}{(x^2 + 1)^{5/2}} = \frac{x(x^2+1)}{(x^2 +1)^{5/2}} - \frac{x}{(x^2 +1)^{5/2}} = \frac{x}{(x^2+1)^{3/2}} - \frac{x}{(x^2 +1)^{5/2}}\end{equation*}

.

This trick is literally a life-saver. Sketches worked out okay, I cut myself 2 marks just to be on the safe side for some lack of justification of my sketches. :dontknow: 18 marks and 27 minutes.

Q2: Looked like an okay question, bit fiddly and I overkilled b (iii) by using a contradiction instead of a counter example which annoyed me as that meant I hadn't fully gotten a grasp of the concept introduced. I mis-read one part of the question and forgot to evaluate f(180)f(180) but was advised to cut only one mark for that, but I'm going to cut two just to be safe. 18/20 and 25 minutes.

Q14: Bit of a weird question, my method was slightly wonky and I didn't quite get there. So I'm giving myself 10/20, I spent forty minutes on it as well...

Q12: I tried the first part, got that, gave myself 5/20 and then gave up because I had no clue what the rest was asking of me. :lol:

Q11: Not a bad question, I've never done a pulley one on STEP before but this was surprisingly tame, the algebra was quite ugly and it was quite partial-y. Managed 13/20 in 20 minutes.

Overall thoughts: Not bad. Wish I'd been able to do more questions, not during the mock but as being able to attempt them tomorrow or something; but I don't think any of the remaining questions are accessible to me, which isn't a very good sign. Fairly okay though. III 2005 to be done soon, probably next week. :yep:
Original post by Zacken
STEP II, 2005:


Trying really hard not to say anything mean/sarcastic. Well done dumbo you're the cleverest, super impressed :yep:

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Reply 1188
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Zacken
OP
22
Original post by tinkerbella~
Trying really hard not to say anything mean/sarcastic. Well done dumbo you're the cleverest, super impressed :yep:

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Pity, I quite enjoy your mean/sarcastic comments. Thanks fatso. :yep:

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Original post by Zacken
STEP II, 2005:

Total time: 2:50.
Total mark: 109.


only just realised you're wearing glasses in that picture,huh,
anyway what do you use to mark your papers? doing my first full one on saturday and would like to know what grade/mark it would translate too, nice work btw
Original post by Zacken
STEP II, 2005:

Total time: 2:50.
Total mark: 109


Very nicely done, especially on that integral trick :colone:

A question I've always had - how do you mark STEP papers, seeing as there's no marking guide?
Original post by Infinity999
@physicsmaths and @Zacken https://www.youtube.com/watch?v=Zvm8SjCNKgEFrom 6:24 and onwards, is the way he is doing it correct? Shouldn't he be using the Quotient Rule? I have no idea what he's done there.
Original post by Zacken
What the **** is this guy doing? His "simplification" at 6:23 is all wrong, he shouldn't be allowed to do maths...
he made it private so I cant see it :frown: what did he do? (if its easy to explain, i'm curious)

Original post by Zacken
STEP II, 2005:
Total time: 2:50.
Total mark: 109.


sick job btw :biggrin:
Reply 1192
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Zacken
OP
22
Original post by DylanJ42
he made it private so I cant see it :frown: what did he do? (if its easy to explain, i'm curious)

sick job btw :biggrin:


He did something of the form "we want to differentiate ab+c\frac{a}{b+c}, so let's simplify this into ab+ac\frac{a}{b} + \frac{a}{c} then differentiate". I commented on the video and he spotted the error and deleted the video. :lol:

Thanks. :-)
Reply 1193
Avatar for Zacken
Zacken
OP
22
Original post by drandy76
only just realised you're wearing glasses in that picture,huh,
anyway what do you use to mark your papers? doing my first full one on saturday and would like to know what grade/mark it would translate too, nice work btw


If you want, I don't mind you scanning your answers in and letting me have a look to see if I agree with your marks. But really, I just look at the solutions and practise has given me intuitive feel as to how the marks are distributed as well as studying the existing mark-schemes for 2011, 2014 and 2015. Most of the time, my solution tends to be fully correct, so that's an easy 20/20. When it's not, then I look for the method/accuracy marks to cut off, stuff like that. But it's basically mostly guesswork. :tongue:

Original post by aymanzayedmannan

A question I've always had - how do you mark STEP papers, seeing as there's no marking guide?
Original post by Zacken
Pity, I quite enjoy your mean/sarcastic comments. Thanks fatso. :yep:

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I enjoy them too, I'll go back to being mean now yay

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Reply 1195
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Zacken
OP
22
Original post by tinkerbella~
I enjoy them too, I'll go back to being mean now yay

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By the way, your script was: "I could never be mean to you <3". You're not doing a very good job fatso

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Original post by Zacken
By the way, your script was: "I could never be mean to you <3". You're not doing a very good job fatso

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Just another thing that I can't do right :cry2:

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Original post by Zacken
If you want, I don't mind you scanning your answers in and letting me have a look to see if I agree with your marks. But really, I just look at the solutions and practise has given me intuitive feel as to how the marks are distributed as well as studying the existing mark-schemes for 2011, 2014 and 2015. Most of the time, my solution tends to be fully correct, so that's an easy 20/20. When it's not, then I look for the method/accuracy marks to cut off, stuff like that. But it's basically mostly guesswork. :tongue:

thanks for the offer, ill give it a go marking it myself and if i cant figure it out ill send it over, a warning in advance: @aymanzayedmannan handwriting is infinitely better than mine, so it could be a bit hard to read:colondollar:
Original post by Zacken
...


Could you help me decompose ∫x2x4+1dx\int \frac{x^{2}}{x^{4}+1} \mathrm{d}x?
Original post by Zacken
He did something of the form "we want to differentiate ab+c\frac{a}{b+c}, so let's simplify this into ab+ac\frac{a}{b} + \frac{a}{c} then differentiate". I commented on the video and he spotted the error and deleted the video. :lol:

Thanks. :-)


oh noo :facepalm: thats as bad as, if not worse than, the mistake that (a+b)2=a2+b2 \displaystyle (a+b)^2 = a^2 +b^2 :laugh:

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