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Consecutive integers

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420024
 Post subject: Consecutive integers
 Post Posted: Thu Feb 21, 2008 10:29 pm 
[Deleted because poster did not cite author.]
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th3414
 Post subject:
 Post Posted: Sun Feb 24, 2008 4:10 pm 
(100 + 150)/2=125 Mult 125*51(sum of #of terms +1)=6375

125-150/2=137.5, then 137.5*26=3575

6375-3575=2800

100+124/2=112, then 112*25=2800

I am just learning this too but i hope it helps!
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Guest
 Post subject: Re: Consecutive integers
 Post Posted: Wed Feb 27, 2008 5:47 pm 
420024 wrote:
[Deleted because poster did not cite author.]



The sum of the consecutive integers from 100 to 150 can be written as

(100)+(100+1)+(100+2)....(100+50)


The sum of the consecutive integers from 125 to 150 can be written as

(125)+(125+1)+(125+2)...(125+5)


We know that the 125 is the same as (100+25) so when you subtract the terms you will cross out everything after this entry to see whats left.


(100+25)+(100+26)......(100+50) Subtract (125)+(125+1)....(125+25)


All that you will have left over is:

(100)+(100+1)+(100+2)....(100+24) because we crossed out everything equal to 125 and everything after it.


Therefore it is equal to the sum of the consecutive integers from 100 to 124.
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StaceyKoprince
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 Post Posted: Tue Mar 04, 2008 1:35 am 
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ManhattanGMAT Staff


Posts: 6064
Location: San Francisco
please cite the author of the problem; otherwise it will be deleted. Thanks!

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