Standard Math Q+A Thread

[Gregs]

Thanks for the help guys!

[jamonwindeyer]

Thanks for the help guys!

No problem! 

[nouribrahim]

 Can someone please explain how to solve this question?

[studybuddy7777]

Ok so the figures on the graph represents $1. The compounding period is every 6 months. So you half the %pa (4% i think / 2 = 2%) Then you look at the periods. 2 years = 4 periods. Then you simply line up the 2% 4 years period and times it by $25000

Hope I could help! Any further questions feel free to ask!

[nouribrahim]

I believe the answer is 330 but the marking guide says its C
can someone explain why please?

[RuiAce]

I believe the answer is 330 but the marking guide says its C
can someone explain why please?

Draw a compass (North-South-East-West) from B.

You're probably looking at it from the wrong perspective. Don't use the NSEW given in the diagram.

It's the bearing of A, from B.

Edit: Since Jake said it was hard without a diagram I just generated one using paint and the original image here.

[jakesilove]

I believe the answer is 330 but the marking guide says its C
can someone explain why please?

Hey!

So it is kind of hard to do this without drawing a picture, so I'll try describe how to get to the answer, and hopefully you can draw it to understand it better.

First, let's draw a North-South line at B. This will be parallel to the N line going through A. The bearing we are looking for is the angle between the new line NB (north line at B), going clockwise, until it hits the line AB.

Now, we know that the angle going straight from North to South at B is 180 degree (just a straight line). So, the only angle left over to figure out is the angle between the line going South from B, and the line AB. But, we can use our angle theorums to figure that out! We know that, by alternate angle on parallel lines, the angle NAB will be equal to the angle ABS (this makes way more sense when you draw it!). So, the final angle that we are looking for is 30 degree. Therefore, the total bearing will be 180 degrees plus 30 degrees, resulting in 210 degree (Making the answer C!)

Jake

[kmorritt]

Hey,

I've been struggling with this one question for Spherical Geometry.
I was wondering if I could get some help with it? The answer is meant to be 10 500km.

Thanks,
Katie

Q. 
It is possible to fly from Perth (32oS, 115oE) to Tierra del Fuego (54oS, 65oW) on the southern tip of South America by doing directly over the South Pole along a line of longitude. Calculate the great circle distance between Perth and Tierra del Fuego (nearest km)

[jamonwindeyer]

Hey,

I've been struggling with this one question for Spherical Geometry.
I was wondering if I could get some help with it? The answer is meant to be 10 500km.

Thanks,
Katie

Q. 
It is possible to fly from Perth (32oS, 115oE) to Tierra del Fuego (54oS, 65oW) on the southern tip of South America by doing directly over the South Pole along a line of longitude. Calculate the great circle distance between Perth and Tierra del Fuego (nearest km)

Hey Katie! So the formula you need is:



So in this case r is taken as 6400km, from you reference sheet, just the radius of the earth. The hard bit is the angle. Let's consider what is happening here.

The plane (or equivalent airborne vehicle thing) needs to fly down through the south pole and then back up to Tierra Del Fuego. To get to the south pole, it flies from 32 degrees south, to the south pole, that's an angular distance of 90-32=58 degrees, because the south pole is 90 degrees. Then, it flies UP to Tierra Del Fuego, and this is a distance of 90-54=36 degrees.

Add these together to give an angle of 94 degrees, then solve!



I hope that helps

[kmorritt]

Thank you Jamon, this has helped me a lot

Hey Katie! So the formula you need is:



So in this case r is taken as 6400km, from you reference sheet, just the radius of the earth. The hard bit is the angle. Let's consider what is happening here.

The plane (or equivalent airborne vehicle thing) needs to fly down through the south pole and then back up to Tierra Del Fuego. To get to the south pole, it flies from 32 degrees south, to the south pole, that's an angular distance of 90-32=58 degrees, because the south pole is 90 degrees. Then, it flies UP to Tierra Del Fuego, and this is a distance of 90-54=36 degrees.

Add these together to give an angle of 94 degrees, then solve!



I hope that helps

[aimbotted]

In the Maths Lecture powerpoint from the Notes section is the answer to question 22 incorrect?

The answer is supposedly $1622 but shouldn't it be $1209.5?

[jamonwindeyer]

In the Maths Lecture powerpoint from the Notes section is the answer to question 22 incorrect?

The answer is supposedly $1622 but shouldn't it be $1209.5?

Hey hey! That is correct based on a quick check, and the HSC solutions seem to match must have been a typo!

Edit: I chatted to Steph (our General Math lecturer), during the lecture she used the new 2.0% Medicare Levy instead of the 1.5% in the question, which leads to the answer on the slides (just for clarity for anyone reading this who went to the lecture and is like "wot")

[kmorritt]

Hi,
Could I please have some help with this question from spherical geometry.
Thank you

[jamonwindeyer]

Hi,
Could I please have some help with this question from spherical geometry.
Thank you

Hey! So remember the conversion rate of longitude to time:



Now to move from Houston to Kabul, we go:



Now as we are moving to the east, our time is increasing, therefore:



Hope that makes sense! It's been a while since I've done time zones

[studybuddy7777]

Sorry this is more of an administration question, but why doesnt any general maths questions come up on my unread topics board page thingy or sidebar?

Seeing as im a mod i want to try to contribute as much as possible!