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The Best Approach to tackle Problems involving 7 as divisor

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farukh_a
 Post subject: The Best Approach to tackle Problems involving 7 as divisor
 Post Posted: Tue Jul 27, 2010 2:35 am 
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Students


Posts: 7
In the MGMAT Number Properties Strategy Guide, no rule is listed for divisibility by 7.

There is another comment at the end of page 14:

"The simplest way to check for divisibility by 7, or by any other number not found in this list is to perform long division"

Does this mean that MGMAT suggests that all those rules that we see on different blogs etc are actually way too cumbersome and time consuming to be practically useful on GMAT?

PS: I can understand that mostly all these rules that we see on the internet are very complex but I just wanted MGMAT's take on this so that I don't waste time remember those intricate formulas that in the end would cost me more time.

Regards
Farukh
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gpinder77
 Post subject: Re: The Best Approach to tackle Problems involving 7 as divisor
 Post Posted: Thu Jul 29, 2010 7:37 pm 
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Students


Posts: 2
farukh_a wrote:
In the MGMAT Number Properties Strategy Guide, no rule is listed for divisibility by 7.

There is another comment at the end of page 14:

"The simplest way to check for divisibility by 7, or by any other number not found in this list is to perform long division"

Does this mean that MGMAT suggests that all those rules that we see on different blogs etc are actually way too cumbersome and time consuming to be practically useful on GMAT?

PS: I can understand that mostly all these rules that we see on the internet are very complex but I just wanted MGMAT's take on this so that I don't waste time remember those intricate formulas that in the end would cost me more time.

Regards
Farukh


for 7, simply double the last digit and subtract it from the digits in front of it.

so for example....is 140 divisible by 7? 0x2=0. 14-0=14. and 14 is divisible by 7, therefore so is 140
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tim
 Post subject: Re: The Best Approach to tackle Problems involving 7 as divisor
 Post Posted: Sat Sep 04, 2010 10:12 pm 
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ManhattanGMAT Staff


Posts: 1779
Location: Southwest Airlines, seat 21C
nice trick, but yes in general it's best not to waste a bunch of time memorizing obscure tricks when they won't save you much time anyway..

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Tim Sanders
Manhattan GMAT Instructor
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