SCHOOL CERT! Math free response last question (1 Viewer)

[Thophie]

no worries
im just happy im not the only one here that appears to have got that wrong =="

 

[manutd12]

no worries
im just happy im not the only one here that appears to have got that wrong =="

Man that question did my head in. Severly but I got that whole quotation crap so we shall see how i went.

 

[gunsforshow182]

I guess I'm in trouble for guessing about 80 percent of the whole exam? ruhoh

 

[supre]

I have STUFFED UP my maths exam soo bad because i went blank half way through it.
i am guessing my raw mark would be close to 50-60/100. can someone estimate which band i would be getting with that sort of raw marks.

 

[mirakon]

I put n^3+(n=1)^3+(n-2)^3...+(n-n)^3

But this is the proper answer got this from Brent012

Would never have thought dat =/

Well, to prove the MHS and RHS from the LHS does require mathematical induction which is a 3 unit topic (when you learn it it's quite simple but the fact is not that many Year 10's know of mathematical induction) so I assume that the LHS which many people put as their solution is the acceptable answer in the SC.

If you're still interested I could post a full proof sometime of the above equations but may take a while.

 

[chakibu]

Do you think I'd get a mark for something terribly stupid like

n^3 + (n-1)^3 + (n-2)^3 ... until zero is reached?

 

[mirakon]

Do you think I'd get a mark for something terribly stupid like

n^3 + (n-1)^3 + (n-2)^3 ... until zero is reached?

Is that exactly how you put it, because it lacks mathematical elegance. It's convention that you count from 1 to n not n to 0. Nevertheless, depending on how much the question was out of I'd guess you obtained a fair few marks, especially if you had working.

 

[Ligawulf]

The answer i got was (n(1/2n+0.5))^2

This was by working out btw during the exam....took about 30 min

I worked it out by realising that all the answers were square numbers
eg
1^3 + 2^3 + 3^3 = 36 = 6^2

This led me to try and find out how to get to the number squared from n

to work this out i divided the squared number by n and i found i always got a number which was half of n plus 0.5

So putting that in an equation, (n(where it was divided by n)*(1/2n + 0.5(the second part of that last sentence)))^2 (square root at the start)

which without the working = (n(1/2n + 0.5))^2

Nobody else had given a clear explanation of how the answer was worked out....this is a method using patterns to help, there are probably other more complex and efficient ways, but this got there in the end...after half an hour

I am the only math excellerant in my school and am i have just started year 12 work, this was my second go at school certificate....96% last time....beat the entire year 10 when in year 9....fingers crossed for 100% this time

 

[khorne]

This led me to try and find out how to get to the number squared from n

to work this out i divided the squared number by n and i found i always got a number which was half of n plus 0.5



which without the working = (n(1/2n + 0.5))^2

those two statements contradict:

if you take your 36 example...36/3 = 13, which is not half of blah blah

Additionally, the formula contradicts what you said, as it is saying half of n multiplied by (n+1), and then all squared.

So, this leads me to believe there is no way in hell you could make that inspection on the spot.

gg khorne, gg

 

[Ligawulf]

those two statements contradict:

if you take your 36 example...36/3 = 13, which is not half of blah blah

Additionally, the formula contradicts what you said, as it is saying half of n multiplied by (n+1), and then all squared.

So, this leads me to believe there is no way in hell you could make that inspection on the spot.

gg khorne, gg

the 36 example placed into the formula
(3(1.5+.5))^2
(3(2))^2
6^2
36

working backwards
sqrt 36 = 6
6/2 = 3
2 = 3/2 + 0.5

may i ask you to check properly whether the formula works?

also, i could not tell how i contradicted myself, but the only thing i can give you is my word that i did this in the exam, as i said, i finished the rest of the exam with 45 or so mins to go, and when i had worked this out i had 15 or so....choose to believe me or not, i did it, and i was bloody proud of myself

and with what i said contradicting itself, i wrote that as i thought it, and as far as i could tell that was my thought process....may i ask what your answer was??

 

[khorne]

sqrt 36 = 6
6/2 = 3
2 = 3/2 + 0.5

n is three...

Your equation is right, but wording is terrible

As for my answer, I didn't do the exam...

but I would consider summation from r =1 to n or r^3

 

[favorite_colour]

i didnt get that at all but really who cares its only the sc.
and like they say it was only one mark...

1mark​

 

[brent012]

If he is truly accelerated and doing year 12 maths then tbh its not too impressive he managed to work it out... Would have finished everything else super fast and had time to look over more complex things and notice stuff - providing he hasnt already learnt about them already.

Edit: Ah yeah if you read up he spent 30 mins on that question.

 

[Amogh]

no offense but 30 minutes for a one mark question = stupid
if i'd have so much spare time i'd rather recheck the paper.

 

[Ligawulf]

no offense but 30 minutes for a one mark question = stupid
if i'd have so much spare time i'd rather recheck the paper.

bah, already did, the difference between 100% and 99% = 1 mark, and i get a pizza if i get 100%

it was around 30 minutes anyway.....

but i don't know i if i will get the mark...since everyone, including my math teacher, wrote the 1^3 + 2^3 .... n^3 .....

 

[silence--]

i think a lot of people over thought this question. it was a one mark question in an sc exam. the 1^3 + 2^3 ... + n^3 would have been fine since they used a similar notation to describe the squares the previous page.

 

[Official]

i think a lot of people over thought this question. it was a one mark question in an sc exam. the 1^3 + 2^3 ... + n^3 would have been fine since they used a similar notation to describe the squares the previous page.

Yes, this.

 

[Ligawulf]

sqrt 36 = 6
6/2 = 3
2 = 3/2 + 0.5

n is three...

Your equation is right, but wording is terrible

As for my answer, I didn't do the exam...

but I would consider summation from r =1 to n or r^3

well at least i tried to explain how i came to the answer, and how come you didn't do the test?

 

[Ligawulf]

as much as i overthought it....i still felt immense satisfaction at getting that formula
and if i don't get that question right it would be bullshit lol...all that effort...but i had plenty of time to think about it

 

[sci-sam]

By the time I did the last question, I had a brain fart. Didn't do it, who cares. Just one freaking mark.

Dont worry dude, my brain did a fart too.......i guessed it but miraculously i got it rite.