Standard Math Q+A Thread

[jamonwindeyer]

If we use the nPr and nCr calculator functions for probability in the exam what working out do we show? And will we lose any marks?

Just checked with our General lecturer, you:

Write what you put into the calculator itself, then just write what it gives you. No working necessary, and you won't lose marks (if the answer is right of course!)

[kneehaha]

Hey!
I do the General Math course, and have been struggling with Simultaneous equations. No matter how many videos i watch, and questions i attempt, it just doesnt work out for me! I was wondering if there are any tips etc to get this down pat.

[RuiAce]

Hey!
I do the General Math course, and have been struggling with Simultaneous equations. No matter how many videos i watch, and questions i attempt, it just doesnt work out for me! I was wondering if there are any tips etc to get this down pat.

Please expand on your problem or provide examples (stating which method(s) you would like help on) for more advice. Some general advice for the time being:

1. You always have a choice of whether you want substitution or elimination.
2. Your method doesn't have to be the exact same as provided in sample solutions, so long as it still flows correctly and hence gets to the correct answer
3. Make sure you understand how the elimination and substitution method works.


Edit: Incorporated Jamon's comment since they're always linear

[jamonwindeyer]

Hey!
I do the General Math course, and have been struggling with Simultaneous equations. No matter how many videos i watch, and questions i attempt, it just doesnt work out for me! I was wondering if there are any tips etc to get this down pat.

Hey!! A few tips from our General lecturer:

- Use the method you are more comfortable with (though know both in case they specify a method)
- When in doubt, just get one of the equations to the point where it has \(y\) as the subject - You can then use the substitution method to substitute this equation into the other
- If using elimination method, get all your variables on one side and look for the same value in both equations, eg, a \(2x\) appearing in both. That is the clue for using the elimination method, and you just subtract the equations (if they are the same sign) or add the equations (if they are different sign, \(2x\) versus \(-2x\) for example)

Also remember that we solve these equations to find a point of intersection, so make sure you provide both the \(x\) and \(y\) coordinates clearly at the end I think this is very much a practice makes perfect thing!

2. When they are all linear terms (e.g. \(2x+3y=4\) and \(6x-y=-12\) then you always have a choice of whether you want substitution or elimination.

All of your equations in the General Course will look like this, there are no non-linear terms like \(x^2\) or anything like that

[jamonwindeyer]

2. Chloe holds a provisional license. Her allowable Blood Alcohol Content (BAC) to drive is zero. She knows that the liver breaks down alcohol at an average rate of 0.75 standard drinks per hour. If she consumed 10 standard drinks from 10pm to 2am what is the earliest time that she could legally drive to work?
A. 11.20 am
B. 11.33 am
C. 3.20 pm
D. 3.33 pm
    So since there is no mass I don't know what her BAC is. Am I supposed to work out her weight first and then continue or?

Hey! Sorry this took a while but I wanted to run it past Steph - This is actually a bit of a trick, because we aren't given the standard info we just use some intuition. We know she starts drinking at 10pm, and can break down 0.75 standard drinks per hour from that point. She needs to break down 10 drinks - This takes:



So if we count forward this much from 10pm, we get 11:20am - The answer should be A

[morning_sunshine]

Ok so not sure if this question has been addressed but if its asking for what amount can be picked out of the jar why id it 4/37 when there is 37 in his hand?

It just confuses me

[jamonwindeyer]

Ok so not sure if this question has been addressed but if its asking for what amount can be picked out of the jar why id it 4/37 when there is 37 in his hand?

It just confuses me

Hey! So when he grabs that handful, it is representative of the amount of coins total in the jar. So the probability of finding a gold coin in the jar is the same as finding it in his hand - It's random sampling

So that is why it is \(\frac{4}{37}\), because the sample is representative of the population, so to speak

[morning_sunshine]

Hey! Sorry this took a while but I wanted to run it past Steph - This is actually a bit of a trick, because we aren't given the standard info we just use some intuition. We know she starts drinking at 10pm, and can break down 0.75 standard drinks per hour from that point. She needs to break down 10 drinks - This takes:



So if we count forward this much from 10pm, we get 11:20am - The answer should be A

THANK YOUUU SO MUCH CLEARER NOW
It really did trick me

[Rainbowhippocampus]

Hi there, just wondering how to calculate monthly repayments?  Is there a formula for it?

[jamonwindeyer]

Hi there, just wondering how to calculate monthly repayments?  Is there a formula for it?

I think I know the question type you mean, and you are always given an annuities table for an annuities type question. You use the table

Did you have an example of something you are struggling with?

[Rainbowhippocampus]

I think I know the question type you mean, and you are always given an annuities table for an annuities type question. You use the table

Did you have an example of something you are struggling with?

2010 HSC
mark needs $8000 for a holiday in three years time.  He has a holiday savings account with a balance of $600. He arranges to deposit $150 into this account at the end of each month for the next 3 years.  He earns 6% per annum interest on the money in the account (book says to change this to 39.3361), compounded monthly.  Will mark have enough money for his trip at the end of three years?  Justify your answer with suitable calculations.   
These are the sorts of Qs catching me off guard

[harry77]

hello

i need help with this question pls, i am a little confused as to working this out

thanks 

[RuiAce]

hello

i need help with this question pls, i am a little confused as to working this out

thanks 

This one was answered quite recently

[harry77]

thanks sorry missed the solution before

[britt.jayne]

Hi.... 
This is probably a dumb question but i can't understand why the answer for the attached question is A? I got B and can't quite figure out why it is A...
Thanks heaps... very much appreciated!!!!!!!....