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#1 2006-06-16 04:40:06

pal2006
Guest

fill the series

2,3,10,39,172,?
what will be the next no.?and how?

#2 2006-06-16 04:57:55

luca-deltodesco
Member
Registered: 2006-05-05
Posts: 1,470

Re: fill the series

pal2006 wrote:

2,3,10,39,172,?
what will be the next no.?and how?

ive tried loads of things, but im stumped


The Beginning Of All Things To End.
The End Of All Things To Come.

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#3 2006-06-16 05:30:44

Ricky
Moderator
Registered: 2005-12-04
Posts: 3,791

Re: fill the series

And so is the online encyclopedia of integer sequences.  Where is this sequence coming from?  A math textbook?  A teacher?  You just put a bunch of numbers next to each other?


"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

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#4 2006-06-16 06:52:22

pal2006
Guest

Re: fill the series

This Question Is From One Of The Question Banks Of M.b.a

#5 2006-06-16 11:57:09

MathsIsFun
Administrator
Registered: 2005-01-21
Posts: 7,550

Re: fill the series

Maybe not an integer sequence ... could be real numbers and the sequence is exponential.


"The physicists defer only to mathematicians, and the mathematicians defer only to God ..."  - Leon M. Lederman

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#6 2006-06-16 14:25:48

Ricky
Moderator
Registered: 2005-12-04
Posts: 3,791

Re: fill the series

Huh?  All of the numbers given are integers.  Are you suggesting the numbers on down the line can be decimals?


"In the real world, this would be a problem.  But in mathematics, we can just define a place where this problem doesn't exist.  So we'll go ahead and do that now..."

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#7 2006-06-18 01:03:49

jukka
Guest

Re: fill the series

The answer is veeeeery logical and in my opinion very simple... You just have to see those numbers in a different way,





If u still havent found what u are looking for:
SPOILER!!!










Try to add two of numbers with eachother...

#8 2006-06-18 02:42:19

numen
Member
Registered: 2006-05-03
Posts: 115

Re: fill the series

jukka, I thought I had it too. But it doesn't work with the last number 172, I get it to something else hmm am I missing something?

Edit: Nevermind, I got it now big_smile

Last edited by numen (2006-06-18 03:00:45)


Bang postponed. Not big enough. Reboot.

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#9 2006-06-18 04:58:59

luca-deltodesco
Member
Registered: 2006-05-05
Posts: 1,470

Re: fill the series

numen wrote:

jukka, I thought I had it too. But it doesn't work with the last number 172, I get it to something else hmm am I missing something?

Edit: Nevermind, I got it now big_smile

well i dunno about the nevermind, but when i first posted, i thought i had got it with adding the numbers via

u[n] = (n-1)(u[n-1]+u[n-2])

i.e

u[3] = 2*(2+3) = 10
u[4] = 3*(10+3) = 39
u[5] = 4*(39+10) = 186 =/= 172, and then i realised it was wrong

so what is the answer


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The End Of All Things To Come.

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#10 2006-06-18 07:38:03

numen
Member
Registered: 2006-05-03
Posts: 115

Re: fill the series


Bang postponed. Not big enough. Reboot.

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