If you want any help with maths, ask me here

thetalker · 08-06-2017 9:23pm

roisiny wrote: »

The differences when using the two are probably like 40€ in 100,000, but is there any reason for using the first over the ones used in log tables? Thanks

I did some examples just to be sure but there is no difference, in one you are dividing

(ar^n - a)

(r - 1)

And the other is

(a - ar^n)

(1 - r)

It might not be apparent but really all you're doing when you subtract is finding the difference between the numbers, so when you do it the other way around all thats changed is the signs, so (a - arn^n) is negative.
But since you divide by another negative number the answer is positive.

A97 · 08-06-2017 9:24pm

Those two equations are completely equivalent if I'm not mistaken. You're essentially negating the top and the bottom, so two negatives make a positive. There shouldn't be a difference between the answers, except for rounding which often occurs in financial maths.

You should either use all of the decimals your calculator gives you, or if you know how, store them in your calculator. Don't try to learn this now if you don't know how. Writing down all 9 or so decimals from your calculator will give the same answer.

I doubt you'd lose too many marks, but this is an important section to keep as many figures as possible, since a lot of money can accumulate over say, 40 years.

Ponguin · 08-06-2017 11:01pm

A97 wrote: »

No worries. I'm pretty sure that you wouldn't be asked to integrate an exponential that is multiplied by the variable and is raised to the variable too e.g. xe^x, unless it was asked in a manner like that example was. Just be sure that you can integrate any type e raised to a variable such as:

e^-x dx
e^(3t+5) dt

As you probably know, differentiate the exponent, and divide by that derivative. Add a constant of integration if needed. .

Really sorry but would you be able to explain this a little further

daraghwal · 08-06-2017 11:06pm

Account Number wrote: »

Can someone help me with part (ii) prove logbase5 24 = (3a + b) over (1-a)
when a = logbase10 2 and b = log base10 3?? I have up to logbase10 24 over logbase10 5 and am lost cos the change of base doesn't work?? Sorry about the way I laid it out in the post,have no clue where half the buttons are on a laptop keyboard.

Could someone do out this in full please? I wasn't able to do it with the solution that was already given. Thanks!

daraghwal · 08-06-2017 11:17pm

Ponguin wrote: »

Really sorry but would you be able to explain this a little further

Solution:

EDIT: DON'T FORGET THE + C AT THE END AS THE CONSTANT OF INTEGRATION! AAAAARRRGGGHHHHHHHH!!!

Ponguin · 08-06-2017 11:20pm

Thanks a mill that clears things up

A97 · 08-06-2017 11:49pm

daraghwal wrote: »

Could someone do out this in full please? I wasn't able to do it with the solution that was already given. Thanks!

See attachments below. I hope it's clear.

daraghwal · 09-06-2017 8:30pm

https://www.examinations.ie/tmp/1497029290_3232988.pdf

Could someone do out 4 (a) to put my mind at ease? Also what did people get for a and b on question 6 and what did people get for the end of question 9 (c)

I know post mortems aren't good but it's just to put my mind at ease. Thanks in advance!

I think I got 10 for 4 (a) for some reason

Beaulieu · 09-06-2017 9:12pm

daraghwal wrote: »

https://www.examinations.ie/tmp/1497029290_3232988.pdf

Could someone do out 4 (a) to put my mind at ease? Also what did people get for a and b on question 6 and what did people get for the end of question 9 (c)

I know post mortems aren't good but it's just to put my mind at ease. Thanks in advance!

I think I got 10 for 4 (a) for some reason

Link isnt working -what level are you talking about?

Liordi · 09-06-2017 9:14pm

https://www.examinations.ie/tmp/1497039240_7753710.pdf

thetalker · 09-06-2017 9:30pm

Does anyone know what page the amortisation proof was in active math, I wanted to see if my attempt was in any way similar but I can't seem to find the page the proof is on

Liordi · 09-06-2017 9:40pm

thetalker wrote: »

Does anyone know what page the amortisation proof was in active math, I wanted to see if my attempt was in any way similar but I can't seem to find the page the proof is on

I couldn't find it in the book earlier and I scanned through the whole financial maths chapter. I'm pretty sure that we had never covered it.

I found it on here though. http://www.projectmaths.ie/documents/modulars/4/FinancialMathsExtraQuestions.pdf

It's on page 14 of this pdf.

thetalker · 09-06-2017 9:49pm

Liordi wrote: »

I couldn't find it in the book earlier and I scanned through the whole financial maths chapter. I'm pretty sure that we had never covered it.

I found it on here though. http://www.projectmaths.ie/documents/modulars/4/FinancialMathsExtraQuestions.pdf

It's on page 14 of this pdf.

thanks, I mentioned the formula but thats about it, I still can't find it in the book, weird. Our teacher never went over it either.

daraghwal · 09-06-2017 11:12pm

Beaulieu wrote: »

daraghwal wrote: »

https://www.examinations.ie/tmp/1497029290_3232988.pdf

Could someone do out 4 (a) to put my mind at ease? Also what did people get for a and b on question 6 and what did people get for the end of question 9 (c)

I know post mortems aren't good but it's just to put my mind at ease. Thanks in advance!

I think I got 10 for 4 (a) for some reason

Link isnt working -what level are you talking about?

Sorry, Higher level. I think links expire but it's up on examinations.ie

Creativ · 09-06-2017 11:31pm

I got 12 days for that Question 4. How about you?

Liordi · 09-06-2017 11:52pm

Creativ wrote: »

I got 12 days for that Question 4. How about you?

I got 13 days for 4A and 16 + 8root2 for 4B.

roisiny · 10-06-2017 12:10am

A97 wrote: »

Those two equations are completely equivalent if I'm not mistaken. You're essentially negating the top and the bottom, so two negatives make a positive. There shouldn't be a difference between the answers, except for rounding which often occurs in financial maths.

You should either use all of the decimals your calculator gives you, or if you know how, store them in your calculator. Don't try to learn this now if you don't know how. Writing down all 9 or so decimals from your calculator will give the same answer.

I doubt you'd lose too many marks, but this is an important section to keep as many figures as possible, since a lot of money can accumulate over say, 40 years.

Thanks for your help (and everyone else that answered my stupidly basic question ðŸ€) had no trouble with financial math (well before whatever they gave us today ...) but didn't want doubt in my mind going in about something that was essentially not even an actual issue!

A97 · 10-06-2017 9:46am

roisiny wrote: »

Thanks for your help (and everyone else that answered my stupidly basic question ðŸ€) had no trouble with financial math (well before whatever they gave us today ...) but didn't want doubt in my mind going in about something that was essentially not even an actual issue!

It's easy to get flustered by things like that around exam time. You see something unusual and you start to doubt yourself. The important thing to remember is that it's probably something simple enough and there is so much that you do know. A place like boards is good as it can help you to clarify things quickly. It can be difficult, but it helps to keep calm when something confuses you. It's difficult but it's easier to solve the problem that way.

chris241111 · 10-06-2017 1:17pm

regarding statistics what is the difference between sigma/rootn and 1/rootn

thetalker · 10-06-2017 3:01pm

Sigma represents the mean, so it's the standard error of the mean, you use it for the 95% confidence intervals involving the mean.

The 1/root n one is the margin of error for a population proportion.
So let's say 20 people out 100 in a sample liked ice cream, that's a proportion of 0.2
The margin of error in that case is 1/10 or 0.1
That's pretty big.
I'm not sure if I got it completely right, but I think that's the gist.

pinkbear · 10-06-2017 5:56pm

chris241111 / thetalker

Explanation of the 3 related formulas attached

carefulnowted · 10-06-2017 5:58pm

If you're asked to explain the meaning of the p-value, what would you say? In my book, it says the p-value is "the lowest value at which we could have rejected the null hypothesis", but the sample paper explanations are much more complicated.

pinkbear · 10-06-2017 6:09pm

carefulenowted:
I think your book definition is fine. Or something like:

"The P value, or calculated probability, is the probability of finding the observed, or more extreme, results when the null hypothesis (H0) of a study question is true."

What do the sample papers say?

pinkbear · 10-06-2017 6:14pm

My notifications had turned off on this thread ages back, so I thought no-one else was posting. I have them back on now, so if anyone has any outstanding questions, please ask and I will definitely answer.

Liordi · 10-06-2017 6:15pm

How is this question done?

pinkbear · 10-06-2017 6:29pm

Liordi wrote: »

How is this question done?

Answer attached

thetalker · 10-06-2017 7:38pm

Q3 b of the 2015 sample papers says the p value is
"This p-value represents the probability of randomly selecting a sample of 100 bulbs
with mean lifetime that is less than or equal to 1475hrs or greater than or equal to
1525hrs, given that the mean lifetime of the bulbs is 1500hrs."

Btw Q2d of that paper uses the margin of error even though we have the standard deviation, that threw me of a bit when doing the Q, any ideas if there's a way to have known the 1/rtn was what they wanted and not the p one.

http://www.mathsdojo.ie/pdf/MS_LCH_P2_2015_Sample.pdf

jogd1234 · 10-06-2017 7:44pm

Hi, just wondering why it is you calculate confidence interval, p-value AND do a hypothesis test (i.e check if z-score is in critical region)? Surlely they're all essentially the same thing, and any one of them can show wha you're looking for? Is it just to show that you can do all three, or is there actually a reason for having to do each of them?

Thanks

daraghwal · 10-06-2017 8:14pm

pinkbear wrote: »

My notifications had turned off on this thread ages back, so I thought no-one else was posting. I have them back on now, so if anyone has any outstanding questions, please ask and I will definitely answer.

Would you mind finding out what the values of a and b are in question 6 and what is the answer for question 9 (c)? They've been bugging me since Friday and I'd just like to see if I got them right or wrong. Thanks!

Take Your Pants Off · 11-06-2017 12:30pm

http://mselkirk.weebly.com/uploads/9/4/7/0/9470803/2015-lc-maths-higher-paper2.pdf.
I know I said this was the last time I'd ask but then I realised im crap at maths.

In the above question 4 part iii.
It says atleast 3. There is lots of ways doing it, one, the long way, get probability of 3,4,5 all up to 20 breaking down, but at that stage exam will be half way done.
Another method I looked at is: 1-(p(2breakdown)+P(none breakdown).
The formula if you may call it, I used it another question that was similar to this and I got the right answer for that, but here its not working.
I know in the m.s. they did 1-p(none more than 2 break down) but I would not have caught that in the exam, so I rather not use that.
Would anyone know a formula for working out with atleast with specific number instead of 1 ?.

If you want any help with maths, ask me here

Comments