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# STEP III this afternoon.... watch

1. (Original post by DonnaB041986)
Yeah I got the same as what I'd got earlier in the question. I really didn't like the rest of the paper though.
do you have any idea roughly how many questions need to be complete/mostly complete to get a grade 2? im sure someone will have asked about that before.

Donna
-x-
According to last year's entrants you need 4 'good' answers to get a grade 2.
2. (Original post by meepmeep)
If you took the sum of 1/r2^r to n=3. you get 1/2+1/8+1/24=16/24=2/3

As ln2=SUMr=1 to r=n of 1/r2^r +In+1, then ln2=2/3+I4 (I think). Weird that you got the harder limit and not the easier one though. That was the weirdest exam in my life though. For the first hour and a half, I literally couldn't do anything. I ended up trying to integrate sechx for about 20 minutes then mucked around with 3 to no avail. I was ready to walk out the exam hall really. Then I thought to myself, I'm never going to do this, at least give a good account of yourself. Then I twigged the difference of two squares in 2 and then it went great from there and I got 4 questions completely finished (2, 6, 7 and 13). I'm confident with my solutions to 2, 6 and 7 and am semi-confident about 13. I went from feeling miserable to great in an hour and a half. If only I;d have stopped running about like a headless chicken and panicking for the first hour and a half!
Mine kind of went solid all the way through. I looked at Q1 for 5 minutes before doing the obvious thing that i would have spotted in 10 seconds if id been doing at home. Finished 1 after 35 minutes feeling pretty good. Then I did lots of 3 before slightly fudging one of the parts. I didn't use the difference of 2 squares anywhere in 2 which worries me. The asymptotes were obvious. Then i differentiated and set f'(x) = 1, to get that x = -1/2. The tangent with gradient 1 at (-1/2, -9/2) was the asymptote. (x+2)^2 was the double root found by factor spotting. The graph sketch was fun, using everything youve jut found out.

Thinking about it, 8 is really easy although I made an incredibly stupid mistake which meant i only got half (if that) of it.
3. I still don't know the solution to q1.. I got int(0,a) [sinhx/cosh2x] but I couldn't see where to go from there.

Maybe another approach... difference of two squares?

http://www.sine-wave.net/stuff/STEP-III-2004-q1.jpg
4. (Original post by Turbonutter)
I still don't know the solution to q1.. I got int(0,a) [sinhx/cosh2x] but I couldn't see where to go from there.

Maybe another approach... difference of two squares?

http://www.sine-wave.net/stuff/STEP-III-2004-q1.jpg
You know what, I did that question I htink perfectly, and I can't really remember how I did it. I think maybe I used a substitution u = cosh x.
5. The very first part can be doing using partial fractions, didn't do the rest though.
6. Aha, u=coshx does indeed work.

As does the difference of two squares.. took me about 10 minutes. Shame I didn't have this insight in the exam.

I swear a cup of tea and Powerslave/Brave New World goes a long way to mathematical enlightenment
7. (Original post by Turbonutter)
Aha, u=coshx does indeed work.

As does the difference of two squares.. took me about 10 minutes. Shame I didn't have this insight in the exam.

I swear a cup of tea and Powerslave/Brave New World goes a long way to mathematical enlightenment
u = coshx in the first
u = sinhx in the second
Take them away and let a-> infinity
U = e^x gives INT 1/(u^4 + 1) du = 1/2 of displayed answer

Did this question quite easily in the exam. Didnt do any other questions as well as i did this one
8. Thanks.

Odd that.. I find the mechanics questions easiest of the lot, whereas most people don't like them at all.

The one with the two strings and a mass was just basic SHM.
9. (Original post by yawn1)
According to last year's entrants you need 4 'good' answers to get a grade 2.
i thought 4 'good' answers got a grade 1? Also, how much of the question do you have to do/get right for it to be good?
10. (Original post by Drederick Tatum)
i thought 4 'good' answers got a grade 1? Also, how much of the question do you have to do/get right for it to be good?
Well if q's are out of 20, you certainly won't need more than 60 for a 1, so 4 good answers should be sufficient. I'd say an answer is good if you do nearly all of it, or do all of it but make a stupid error somewhere, it's the idea that counts

Edit: I missed of a few little things like when cancelling stuff in an inequality in q.4 not saying that i could because they were >0 or in q.3 the graph might not have been very well explained. I'd say my answer is still good but not complete. But i got part (2) and so part(3) of q. 13 wrong because of an arithmetic error, and i'd say it wasn't good, i'd say it was a 'beta', a half complete question...
11. oh dear , i got 3 parabolas in q8, thought it was too good to be true

plus q6 i missed the last part out but my answer to part b was quite good i think (used my formula for 1,2,1,2,1... that came to me in a dream once.... don't ask)

was gona do the SHM one too but thought it might take too long ... do the mechanics ones generally take longer?

didnt even turn the page to the stats q's!!

and in q1 i got the last part to be half of the printed answer too.

did anyone do question 2??? what did you get the left side of the graph to look like???

good luck for tomorrow everyone btw
12. (Original post by stephx)
oh dear , i got 3 parabolas in q8, thought it was too good to be true

plus q6 i missed the last part out but my answer to part b was quite good i think (used my formula for 1,2,1,2,1... that came to me in a dream once.... don't ask)

was gona do the SHM one too but thought it might take too long ... do the mechanics ones generally take longer?

didnt even turn the page to the stats q's!!

and in q1 i got the last part to be half of the printed answer too.

did anyone do question 2??? what did you get the left side of the graph to look like???

good luck for tomorrow everyone btw
Steph, for q.6 part b, surely the answer was obvious.

if v(n) = 1 for n even and 2 for n odd

then v(n+1)^2 + v(n)^2 = 5 = 4.v(n).v(n+1) - 3, since one of v(n) = 2 and the other is 1?
13. (Original post by beauford)
Well if q's are out of 20, you certainly won't need more than 60 for a 1, so 4 good answers should be sufficient. I'd say an answer is good if you do nearly all of it, or do all of it but make a stupid error somewhere, it's the idea that counts

Edit: I missed of a few little things like when cancelling stuff in an inequality in q.4 not saying that i could because they were >0 or in q.3 the graph might not have been very well explained. I'd say my answer is still good but not complete. But i got part (2) and so part(3) of q. 13 wrong because of an arithmetic error, and i'd say it wasn't good, i'd say it was a 'beta', a half complete question...
So how many marks out of the 20 do you think you would get for a beta, say your question 13 for example?
14. (Original post by Drederick Tatum)
So how many marks out of the 20 do you think you would get for a beta, say your question 13 for example?
Depends i'd say you're looking between 10-15. Apparently, i'm not certain if this is true, the paper is actually marked out of 150 and if you score over 15 for a question, the marks over 15 you score are doubled (i.e 16 -> 17, 17-> 19... 20 -> 25). I don't know if this is true though. I think if you miss out a bit you'll lose more marks than if you do it with the right idea but get the wrong answer.
15. (Original post by beauford)
Steph, for q.6 part b, surely the answer was obvious.

if v(n) = 1 for n even and 2 for n odd

then v(n+1)^2 + v(n)^2 = 5 = 4.v(n).v(n+1) - 3, since one of v(n) = 2 and the other is 1?
well, i ended up with 2^2 + 1^2 = 5 i think !

has a 5 in there somewhere right!

ran out of time for part c though, should of just stuffed something down even if it was a load of crap. better than leaving it blank, i hate leaving stuff blank what was the answer to part c?
16. (Original post by stephx)
well, i ended up with 2^2 + 1^2 = 5 i think !

has a 5 in there somewhere right!

ran out of time for part c though, should of just stuffed something down even if it was a load of crap. better than leaving it blank, i hate leaving stuff blank what was the answer to part c?
I think the answer to part c was 1,2,7,2,1,2,7,2....
17. (Original post by beauford)
I think the answer to part c was 1,2,7,2,1,2,7,2....
hmm, wonder if id have got that if id had more time?? probably not...

what i did of q6 was basically stuffed into the last 25 mins of the exam so i spose any marks are better than nothing...

was thinking about paper 3 all last night though, got really bad insomnia, didnt get to sleep til about 1 and had to get up at 6:30... needless to say i didnt give my best performance today

cant see either of my papers being higher than a 2 now to be honest .... oh dear *hoping im wrong and that the grade boundaries are low*
18. Can anyone give me an idea of how I did? I'm an American trying to do maths at Robinson College, Cambridge, and my offer is 1, 2 in STEP 2 and 3 respectively. I did 2, 3, 6, 7, 8 on STEP 3 as follows:

2. I did the whole thing, but half of my sketch was upside down due to copying something down from the first part of the question with an extra minus sign. Does that kill my answer or is it no big deal?

3. I got the desired inequality, and I don't think there was any smoke and mirrors in my proof, although the second inequality they ask you to prove I did in a completely different way from the one suggested.

6. I got 1, 2, 7, 2 etc.

7. I got the inequality by using n = 3 -- does this sound about right?

8. I only did a third of this one (the first half) because I ran out of time. Will I get much credit for it?

Can I get a 2 out of that? Thanks very much.
19. (Original post by royalchicken)
Can anyone give me an idea of how I did? I'm an American trying to do maths at Robinson College, Cambridge, and my offer is 1, 2 in STEP 2 and 3 respectively. I did 2, 3, 6, 7, 8 on STEP 3 as follows:

2. I did the whole thing, but half of my sketch was upside down due to copying something down from the first part of the question with an extra minus sign. Does that kill my answer or is it no big deal?

3. I got the desired inequality, and I don't think there was any smoke and mirrors in my proof, although the second inequality they ask you to prove I did in a completely different way from the one suggested.

6. I got 1, 2, 7, 2 etc.

7. I got the inequality by using n = 3 -- does this sound about right?

8. I only did a third of this one (the first half) because I ran out of time. Will I get much credit for it?

Can I get a 2 out of that? Thanks very much.
you may lose a couple of marks on 3 for not following the suggested method, maybe a couple more, i get the same as you for 6 and 7, for two you should lose no more than 7-8 marks i'd think, so you should get a 2 comfortably, perhaps a 1. Like yourself in a way, I did 1 partially, 3,4,6,7 completely and 13 but made a silly mistake in it. You won't get many marks for q.8 in my opinion, maybe 5-6.
20. beauford, can you analyse my STEP 3 as well please?

1. Pretty sure i got all of this - the last inequality was half the printed result.

3. Not sure whether my sketch-proof was great, but question was good from there.

5. Prove the first 2 preliminary results, but didnt do any of the bulk of the question.

7. Did all this reduction formula question except the very last part - proving the inequality.

8. Did all the parts.

14. There were three parts; for the first, i think i did the summation wrong to find the probability, the second was correct but the third part was dependant on the first two, so it was wrong.

Tatum

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