Standard Math Q+A Thread

[jakesilove]

Hello, I'm finding it difficult to understand the trigonometry topic and really need some help solving this math's question.

Hey!

So, on your formula sheet, you get the Sin rule (below)



A, sin(a), B, sin(b), C, sin(c) etc. are shown in the triangle below



The thing to remember is that side A is opposite angle a. So, in your triangle, we would say that theta is opposite the 9cm side, and 48 degrees is opposite the 14cm side.


Aaaaand Rui has beat me to it.

[Snew]

Hello! I just had a question about financial maths - in a credit card question, if there is a 55 day interest period, for example, and the due date for payment is the 25th and the person pays after this date, will they be charged interest for each day of the 55 day interest free period, or will they begin charging each day after this date? Thanks for your time 

[jamonwindeyer]

Hello! I just had a question about financial maths - in a credit card question, if there is a 55 day interest period, for example, and the due date for payment is the 25th and the person pays after this date, will they be charged interest for each day of the 55 day interest free period, or will they begin charging each day after this date? Thanks for your time 

Hey Snew! Welcome to the forums! 

The interest starts AFTER the 25th in your example - The interest free period is just that, interest free! You only pay interest for due amounts after this period 

Hope this helps!! Sorry for the late reply, I wanted to check my answer before I gave it, I didn't do General so wanted to be sure 

[stephanieazzopardi]

Hey Snew! Welcome to the forums! 

The interest starts AFTER the 25th in your example - The interest free period is just that, interest free! You only pay interest for due amounts after this period 

Hope this helps!! Sorry for the late reply, I wanted to check my answer before I gave it, I didn't do General so wanted to be sure 

Hi Snew,

Just clarifying what Jamon has awesomely said; the question will always tell you whether to count or not count the day that you purchased and/or paid for the item as part of your interest-free or non-interest-free periods.
For example, a question from the 2014 CSSA HSC Trial stated this before asking two questions:

On 21 January 2014, Michael used his credit card to purchase $1 350 worth of camping gear. The terms of Michael’s card are:

• No interest free period
• Minimum payment of 2% of the balance owing or $25, whichever is greater
• Simple interest is calculated daily on a period which includes the date of purchase and the date of payment.
• The interest rate for purchases is 13.49% per annum.

So hope that clarifies a few things! Thanks for asking and please make sure you ask us any more questions that you may have - we're happy to help 

[sophroberts812]

Hey guys I have a few maths questions that I need some help with!! They're screenshots from an online test (HotMaths - not sure if you've heard of it). It has the answers just not the working so I'd love if someone could please explain how to get to the right answer!!

Moderator action: Posts merged. At times like this, please combine all the questions in one post to avoid repeat-posting.

[legorgo18]

Hey guys I have a few maths questions that I need some help with!! They're screenshots from an online test (HotMaths - not sure if you've heard of it). It has the answers just not the working so I'd love if someone could please explain how to get to the right answer!!

Hi, for this one, think of it as 2/p (p^-1 is 1/p) + 3
then it will be 2/p + 3p/3
and hence answer is 2+ 3p all over p

Hope i helped

[legorgo18]

Aaaand another one....

For this ratio one, if you are having troubles with powers, try to do this m^4= m * m * m * m
and m^8 = m* m * m * m * m * m * m* m

Cross out the m, it will be none for m^4 hence 1
and there will be m * m * m * m left for m^8 and hence m^4

[legorgo18]

And one more...

For this one, from the info given L (big one) = A(small one) + 500
2/3 A = 1/2 (A+500)
rearranging gives 1/6 A= 250
A= 1500

So L = 1500 + 500
= 2000

[RuiAce]

For this one, from the info given L (big one) = A(small one) + 500
2/3 A = 1/2 (A+500)
rearranging gives 1/6 A= 250
A= 1500

So L = 1500 + 500
= 2000

I'll probably format this one as well

[Snew]

James has just turned 17 and plans on buying a car when he turns 20. He has a part time job and wants to deposit the same amount each quarter in an account earning 12% p.a. compounded quarterly. What amount:
Could be invested now to grow to $12000 in three years at 12% p.a compounded quarterly?
Cheers 

[sophroberts812]

James has just turned 17 and plans on buying a car when he turns 20. He has a part time job and wants to deposit the same amount each quarter in an account earning 12% p.a. compounded quarterly. What amount:
Could be invested now to grow to $12000 in three years at 12% p.a compounded quarterly?
Cheers 

For this one you'd use the future value formula, which is FV = PV (1 + r)^n

And from the question you get the following information...
FV = $12000
r = 3% (12% per annum / 4 quarters = 3% per quarter)
n = 12 (3 years [age 17-20] x 4 quarters per year)

So just sub into the formula...
12000 = PV (1 + 0.03)^12
Rearrange to get PV = 12000 / (1.03)^12

Therefore PV = $8416.56

So James must invest $8416.56 now to have $12000 in three years.


Hope that helps!!!!

[jamonwindeyer]

For this one you'd use the future value formula, which is FV = PV (1 + r)^n
...
Hope that helps!!!!

Legend Soph, thanks heaps for your contribution!

[Kira Leigh]

Hi there
So I understand this is probably a silly question but when do you use the sine rule and the cosine rule? I understand the maths of it just identifying the situation of which to use is what I'm struggling with. Any tips? 

[RuiAce]

Hi there
So I understand this is probably a silly question but when do you use the sine rule and the cosine rule? I understand the maths of it just identifying the situation of which to use is what I'm struggling with. Any tips? 

Usually you get used to when to use what with practice. However, some people do prefer the guidelines as to when to use what rule:

Finding an angle
- Given two sides and an angle - use sine rule
- Given three sides - use cosine rule

Finding a side length
- Given one side and two angles - use sine rule
- Given two sides and one angle - use cosine rule

The guidelines may help at first, but relying on them can be hard because it's easy to mix it up. Which is why with enough practice, people start becoming more reliant on intuition instead.


And there's also the rule of thumb: if one of the two doesn't work, it's most likely the other.

[kneehaha]

Hey!

I had a math test today, which i studied for, however there were so many questions which threw me off and since half yearlies are on its way, i was wondering if i could get any general tips and ways to study effectively for a maths exam, as i want to feel as confident as possible with the HY gen maths exam and not feel like crap after like today ahahah

Thanks