

10272005, 03:14 AM

#1

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Maths Question Driving Me Insane
Hi people
I know this may sound unreasonable making a new thread for this but this is really annoying me ... i really am ticked off because everybody has different answers about it ...
Anyhow, i had my yearly maths exam today ... which is primarily the reason as to why i haven't been on much all of a sudden ... i also have 3 more yearly exams coming up ...
Well ... this is the question ... i personally put 1,000,000 as the answer to this question ... i'm pretty sure that it is but there are like a different answer for every person that i ask
Find n
1 = 1² = 1
1 + 3 = 2² = 4
1 + 3 + 5 = 3² = 9
1 + 3 + 5 + ... + 1999 = n² = n
This is probably pretty basic for you ... but everybody at my school is finding it a weird one ... could anybody please help ?
Thanks in advanced
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10272005, 03:44 AM

#2

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Re: Maths Question Driving Me Insane
Looks like the binomial series. I covered it a couple of weeks ago, but I didn't understand to do just what you're asking, I'm afraid
I can expand an expression like (x+y)^4, but no more than that.
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10272005, 05:22 AM

#3

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Re: Maths Question Driving Me Insane
Well thanks anyways
Anybody else have any ideas about this ?
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10272005, 05:31 AM

#4

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Join Date: Sep 2005
Posts: 26

Re: Maths Question Driving Me Insane
You could also consider this Logic:
(first no+last no)/2 sqr
=((1+1999)/2) sqr= 1000 sqr
Calculate this and you will get your solution.
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10272005, 05:56 AM

#5

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Join Date: Mar 2004
Posts: 8,070

Re: Maths Question Driving Me Insane
OK...
firstly that question is wrong, n^2 != n (but we'll ignore that unless you want to but some cheecky remarks in your book, the only time n^2 = 1 is when n=1).
the sequence is 1+3+5... + k2 + k = n^2
n = k/2+.5
eg, 1 = 1^2 > 1 = 1/2 + .5 = 1 (correct)
1+3 = 2^2 > 3/2 + .5 = 2 (correct)
1+3+5 = 3^2 > 5/2 + .5 = 3 (correct)
1+2+3+...+1999 = 1999 / 2 + .5 = 500,
n=500 and n^2 = 250,000
<edit>
dammit, beaten to it, thats what happens when you answer the phone and have to explain how to share email folders!!!
<edit again>
actually not beaten to it,
like I said, the question is badly written, either me or stacy are squaring the wrong number
this comes frmo the way it's written, n=n^2
dosey maths teachers.
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10272005, 06:47 AM

#6

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Re: Maths Question Driving Me Insane
Wow ... thanks heaps eTechStacy and root This will be EXTREMELY helpful and i can not thank you enough ...
And yes ... maybe i should complain to the teachers about how wrong their equation wrong ... i thought there was something funny about that Thanks heaps again !
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10272005, 07:17 AM

#7

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Join Date: Mar 2005
Posts: 13,091

Re: Maths Question Driving Me Insane
Quote:
Originally Posted by dyserq
Find n
1 = 1² = 1
1 + 3 = 2² = 4
1 + 3 + 5 = 3² = 9
1 + 3 + 5 + x + 1999 = n² = n

Looks like Pythagorean theorem...
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10272005, 07:44 AM

#8

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Re: Maths Question Driving Me Insane
Quote:
Originally Posted by lhuser
Looks like Pythagorean theorem...

Uhh ... Pythagora's Theoram is a²+b²=c² ...
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10272005, 08:00 AM

#9

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Join Date: Mar 2005
Posts: 13,091

Re: Maths Question Driving Me Insane
I know. It looks like...oh...I meant it is similar...
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10272005, 02:02 PM

#10

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Join Date: May 2005
Posts: 2,734

Re: Maths Question Driving Me Insane
Yeah, I noticed that, too. I was like.... wait, n^2 = n?????? WTF? Which n do they want? But yeah, Stacey has it right. The first n would be 1000, and the second n would be 1,000,000 (one million). Root  your logic is correct, but you messed up a bit on your math. 1999/2 + 0.5 = 1000, not 500. Anyway, you guys are basically doing the same thing, just in a different order. Stacy's method is probably a bit easier, but they both work out the same way.
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