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Credit Maths '09 Opinions.

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Meteorshower

For a you have to set h = 0 for when it lands

0 = -2t(t-14)
0= 28t - 2t^2
0= 2t(14-t)

From that t is either 0 or 14. The rocket takes off at t = 0 so it must land at t = 14 meaning it was in flight for 14 seconds

For b you have to know that a parabola is symmetrical, and given that t = 7 is halfway between the two x axis intercepts the height will be the greatest at that point. You substitute 7 for t and see what you get.

edit - (too late :p:

)

Ah the good old days before calculus..

Reply 41

fabulous33

to be honest i really cannot remember what i wrote for part (c) anyway!
hahhaa! but oh well! xx

Reply 42

SmartRoss

Meteorshower: Yes, there was... :smile:

Kirsty59:
You'll probably kick yourself with the rocket question; the number of seconds that the rocket was in flight was the distance between the two roots (i.e. where it met the x axis). When you solve the quadratic equation, you get the roots as 0 and 14, so the rocket was in the air for 14 seconds.

The maximum height of the rocket is the maximum value of the equation. As we know, the roots are 0 and 14. Hence, by symmetry, the x co-ordinate of the maximum point is 7. You then put this into the equation (

h(t) = -2t(t - 14)

), and you get the y co-ordinate; in other words, the maximum heigh. IIRC, that was 98 metres.

EDIT: Dash! Didn't notice the page flips!

Reply 43

namedeprived

Oh my I feel stupid. I can't seem to get that Tn+1 question.

Reply 44

abstraction98

namedeprived

Oh my I feel stupid. I can't seem to get that Tn+1 question.

Have you read my post?

Reply 45

namedeprived

Yes, making me feel more stupid. :biggrin:

I can't seem to understand where you get that forumla from, because if you put values from the sequence in you get

7=(6+(3+1) which is obviously a contridiction.

I'm thinking it might be because I'm unfamiliar with the notation used, completely forgotten most of the stuff.

Some hope I have of Advanced Higher next year!

Reply 46

TheUnbeliever

namedeprived

Oh my I feel stupid. I can't seem to get that Tn+1 question.

The nth term,

T_n

, of the sequence 1, 3, 6, 10...is given by the
formula:

T_n = \frac{1}{2}n(n+1)

(a) Calculate the 20th term,

T_{20}

.
(b) Show that

T_n+1=\frac{1}{2}(n^2+3n+2)

T_n + T_n+1

is a square number.

T_{20} = \frac{1}{2}20(21) = 10(21) = 210

T_{n + 1} = \frac{1}{2}(n+1)(n+2) = \frac{1}{2}(n^2 + 2n + n + 2) = \frac{1}{2}(n^2 + 3n + 2)

T_n + T_{n + 1} = \frac{1}{2}(n^2+n+n^2+3n+2) = \frac{1}{2}(2n^2+4n+2)

= n^2 + 2n + 1 = (n + 1)^2

EDIT: Whoops, forgot brackets in (b).

Reply 47

namedeprived

TheUnbeliever

T_{20} = \frac{1}{2}20(21) = 10(21) = 210

T_{n + 1} = \frac{1}{2}(n+1)(n+2) = \frac{1}{2}n^2 + 2n + n + 2 = \frac{1}{2}n^2 + 3n + 2

T_n + T_{n + 1} = \frac{1}{2}(n^2+n+n^2+3n+2) = \frac{1}{2}(2n^2+4n+2)

= n^2 + 2n + 1 = (n + 1)^2

Oh, so you just substitue n+1 in for n! :biggrin:

Thanks, that was perhaps the most slow dawning realisation I've ever had. I really have no idea what I was trying to do.

Reply 48

MySweetheartTheDrunk

TheUnbeliever

T_{20} = \frac{1}{2}20(21) = 10(21) = 210

T_{n + 1} = \frac{1}{2}(n+1)(n+2) = \frac{1}{2}n^2 + 2n + n + 2 = \frac{1}{2}n^2 + 3n + 2

T_n + T_{n + 1} = \frac{1}{2}(n^2+n+n^2+3n+2) = \frac{1}{2}(2n^2+4n+2)

= n^2 + 2n + 1 = (n + 1)^2

Yayy thats what I done! Although for the last question I left it as n^2 + 2n + 1, realised only one part of that was a square number so re-did working slightly different, got the same and just left it. Until my final check over of the paper where I remembered FACTORISE and got it haha. That parabola question, we've done LOADS of them in class cause they come up quite often and people usually get lost. Had "ZEROES, AXIS OF SYMMETRY, TURNING POINT" drilled into me! Good luck for English tomorrow everyone! Hope some good short story titles come up in writing - spent all day practising short stories, it's all I can write!
x

Reply 49

TheUnbeliever

Just for posterity, I've added in the brackets I obviously missed in (b). This is why I usually do maths on paper and then LaTeX it. :p:

Reply 50

abstraction98

TheUnbeliever

Just for posterity, I've added in the brackets I obviously missed in (b). This is why I usually do maths on paper and then LaTeX it. :p:

That was embarassing..good luck on the 21st.

Reply 51

TheUnbeliever

abstraction98

That was embarassing..good luck on the 21st.

Heh, I think I can live with it. I've committed rather greater mistakes in the past!

Cheers, you too. :-) Planning on ploughing through past papers en masse once I'm on study leave (next Thursday).

Reply 52

SmartRoss

I've just put the Paper 1 questions into the Standard Grade Maths Credit revision area; the only problem is that the LaTeX isn't parsing correctly... I intend to do the same thing with Paper 2 and answers for both papers.

EDIT: Got the LaTeX to work!

Reply 53

abstraction98

TheUnbeliever

Heh, I think I can live with it. I've committed rather greater mistakes in the past!

Cheers, you too. :-) Planning on ploughing through past papers en masse once I'm on study leave (next Thursday).

One more (sensible) period left to go. I've ploughed through them enough times. As you know, if you're doing STEP they are a doddle.

Reply 54

Pelican

Meteorshower

This, combined with the video Sam posted in the mysqa thread, gives me hope that there are those with a sense of humour in the SQA :p:

I know I had a stupid sense of humour when I was 15 but the two electrodes stuck into a lemon in credit chemistry 2007 made me stop for a full five minutes. XD

Reply 55

FuturePilot

namedeprived

Oh, so you just substitue n+1 in for n! :biggrin:

Thanks, that was perhaps the most slow dawning realisation I've ever had. I really have no idea what I was trying to do.

I have to admit that you're not the only one haha. I'm so annoyed now :p:

Reply 56

C274

namedeprived

Oh, so you just substitue n+1 in for n! :biggrin:

Thanks, that was perhaps the most slow dawning realisation I've ever had. I really have no idea what I was trying to do.

I was in exactly the same boat...

Reply 57

Sweet by and by

Paper two was tricky but not hard, bit of a pain tbh. Id learned all my graphs etc and not one was in it! Thought I was prepared knowing it all then it turns out i never even used it! Yeah the standard deviation was a bit confusing, i made it up. Can anyone tell me why it doesnt change?

Reply 58

MySweetheartTheDrunk

Standard deviation is like the range in the prices, how much variation there is between each price - if they're all increasing by the same amount, the variation between them doesn't change. Make sense? Not good at explaining it but I know what I'm TRYING to say. It's basically a different way of asking those questions where they ask you to figure out the standard deviation and mean of a set of data, then give you the SD and mean of another, and tell you to make two valid comparisons between each set. One is it is on average higher/lower, the other is the variation between the data is higher/lower which is based on the SD. Blah, maybe someone else can explain more clearly :P

Reply 59

c.e.stewart

Dose any one have a link to the whole of the credit or/and general mathematics paper?

I'd be greatfull if you could post a copy, message or email one to me.
Cheers!