Mathematics Question Thread

[RuiAce]

Hey guys,

So I have a question on the mark allocation on one of my questions in a test.

The question states 'John has borrowed $200,000. The interest rate is 6% p.a compounded monthly.'
iii.) If John pays $10,000 to the loan each month, find how long it will take him to reduce the loan to $100,000.

I know how to do the question but just made a calculation error saying that 10,000/0.005 was 200,000 instead of 2 million.
My answer is attached; which I can re-write if you can't read it but my teacher wasn't giving me any marks for it which I'm a little surprised about so would love to hear your thoughts.

Which, if you had noticed that, you probably could've saved a few marks by realising something isn't right.

I'm sorry to say but I would not give you any marks either, because I see multiple mistakes; not just the computational one.

[Wales]

Which, if you had noticed that, you probably could've saved a few marks by realising something isn't right.

I'm sorry to say but I would not give you any marks either, because I see multiple mistakes; not just the computational one.

Yeah it wouldn't hurt to ask the teacher for a pity mark but I don't think your chances are too high given you did skip out 4 lines of working. There some things markers can assume but in this case it seems not. Still worth a shot though, fight for that mark.

[12070]

Which, if you had noticed that, you probably could've saved a few marks by realising something isn't right.

I'm sorry to say but I would not give you any marks either, because I see multiple mistakes; not just the computational one.

I didn't even know I missed that last step and had so many chances to realise something isn't right as well. So that is probably fair enough. Thanks for the help in clearing things up though

[Wales]

I didn't even know I missed that last step and had so many chances to realise something isn't right as well. So that is probably fair enough. Thanks for the help in clearing things up though

You clearly know how to do the question. Just try not to skip out any working in the future. Still wouldn't hurt asking the teacher, I fought every mark I thought I had a chance to gain in every exam. It matters!

[katnisschung]

i feel like this is badly worded...

Mohammed's mother invests $200 for him each birthday up to and including his 18th birthday.
The money earns 6% pa How much money will Mohammed have on his 18th birthday
ans$6181.13

also q on small angles how do i find the limit for this...i've only ever seen sinx/x format not this..

3x/sin3x

[f_tan]

Could someone explain why you subtract top curve and bottom curve? Why can't you just integrate sinx?



Mod Edit: Restored deleted post

[Willba99]

Could someone explain why you subtract top curve and bottom curve? Why can't you just integrate sinx?

(Image removed from quote.)

integrating sinx wouldn't find the shaded area under the x axis

[jamonwindeyer]

Could someone explain why you subtract top curve and bottom curve? Why can't you just integrate sinx?

(Image removed from quote.)

Willba is right - Whenever you have an area between two curves, you always find it by taking the integral of top curve minus the bottom curve. This is a blanket rule that works whenever you have a single area bounded between two functions

[Willba99]

hey guys.
so long story short, i bit off more than i could chew with the take-home part of my specialist SAC and i have to solve

192600pi+60000=1254pi(x)+12500sin(pi(x)/100)-40000sin(pi(x)/200)

any help solving this would be greatly appreciated. Basically I'm looking for solutions of something in the form of a=bx+csin(dx)-esin(fx)

[jakesilove]

hey guys.
so long story short, i bit off more than i could chew with the take-home part of my specialist SAC and i have to solve

192600pi+60000=1254pi(x)+12500sin(pi(x)/100)-40000sin(pi(x)/200)

any help solving this would be greatly appreciated. Basically I'm looking for solutions of something in the form of a=bx+csin(dx)-esin(fx)

To be honest, this looks a bit absurd to me; doesn't look like there's a straight forward algebraic fix. I reckon it's more likely that you've made a mistake somewhere along the road. Also, note that this thread is for HSC students; there's a separate one for VCE questions!

[RuiAce]

also q on small angles how do i find the limit for this...i've only ever seen sinx/x format not this..

3x/sin3x

[RuiAce]

i feel like this is badly worded...

Mohammed's mother invests $200 for him each birthday up to and including his 18th birthday.
The money earns 6% pa How much money will Mohammed have on his 18th birthday
ans$6181.13

To be honest, this looks a bit absurd to me; doesn't look like there's a straight forward algebraic fix. I reckon it's more likely that you've made a mistake somewhere along the road. Also, note that this thread is for HSC students; there's a separate one for VCE questions!

Yeah I agree. I'd want to see the progress to that stage before jumping in on it

[Blazeee]

Hey does anyone have an easy acronym or something to remember the justification for similar triangles? It's easy for the congruent triangles with the AAS and SAS and all that...but the similar triangles always tempt me to write these congruence acronyms..which we're not allowed to write 
Thanks!

[RuiAce]

Hey does anyone have an easy acronym or something to remember the justification for similar triangles? It's easy for the congruent triangles with the AAS and SAS and all that...but the similar triangles always tempt me to write these congruence acronyms..which we're not allowed to write 
Thanks!

You really aren't expected to use acronyms at all for similarity. You can develop your own ones to memorise them, however you cannot write them.

That being said, I ignored that. I learnt similarity when I found I could compare them to congruence


The similarity statements can be related to congruence:
- Equiangular: Related to AAS. Just chop out the side.
- All three sides in proportion: Related to SSS. Just replace equal sides with proportional sides
- Two sides in proportion, included angle equal: Related to SAS. Just replace equal sides with proportional sides again.

The tests are honestly almost the same. The only thing is:
- You keep the angles the same, but
- Whenever you have 2 or more equal sides, replace "equal" with proportion.

If you can write down the criteria for congruency, you can then easily write out the criteria for similarity. Force yourself to not use acronyms not permitted

[Blazeee]

You really aren't expected to use acronyms at all for similarity. You can develop your own ones to memorise them, however you cannot write them.

That being said, I ignored that. I learnt similarity when I found I could compare[i/] them to congruence


The similarity statements can be related to congruence:
- Equiangular: Related to AAS. Just chop out the side.
- All three sides in proportion: Related to SSS. Just replace equal sides with proportional sides
- Two sides in proportion, included angle equal: Related to SAS. Just replace equal sides with proportional sides again.

The tests are honestly almost the same. The only thing is:
- You keep the angles the same, but
- Whenever you have 2 or more equal sides, replace "equal" with proportion.

If you can write down the criteria for congruency, you can then easily write out the criteria for similarity. Force yourself to not use acronyms not permitted

Thanks very much!  :)Hopefully i will remember in my exam tomorrow!