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Divisibility

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jkandas
 Post subject: Divisibility
 Post Posted: Fri Feb 26, 2010 8:52 pm 
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Course Students


Posts: 4
Question from MGMAT flash cards:

If the ones digit of an integer is 0, then which (nonzero) one‐digit integers is the integer definitely NOT divisible by?

Answer: None
It could be divisible by any of the one-digit integers! (Except
for 0; dividing by 0 is always off limits.)

To verify, take any nonzero one-digit integer, multiply it by ten, and the
product will end in zero and be divisible by the original one-digit integer.

I do not follow the explanation.

Lets say we choose 60...its not divisible by 7 and 9...how do we generalize this? I understand the explanation that if 6 is multiplied by 10, then 60 will definitely be divisible by 6...but what about 7 and 9...I thought the question asked for other factors that the integer won't be divisible by...

Am I reading the question wrong?
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ronaldramlan
 Post subject: Re: Divisibility
 Post Posted: Tue Mar 23, 2010 10:33 am 
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Students


Posts: 8
Your question is definitely the one that only the author of MGMAT flashcards can answer to.
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mschwrtz
 Post subject: Re: Divisibility
 Post Posted: Wed May 12, 2010 2:22 am 
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ManhattanGMAT Staff


Posts: 506
Yep, misreading the question. Rephrase he question in this way, "What one-digit number is a factor of no number ending in 0?"

You're right, of course, that 60 is not divisible by 7, but 70 is, and it ends with a zero.
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