MGMAT's Number Properties question (Chapter #1)

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MGMAT's Number Properties question (Chapter #1)

by ksear » Mon Nov 15, 2010 10:02 pm
Hi everyone,

I need some help with this question as I'm really confused whether MGMAT's answer is correct (since I have read at several places in this forum that they have made some mistakes in terms of the correct answers). So here it is:

The instructions on top say that all variables in problems #1 through #12 are assumed to be integers unless otherwise indicated.

Question 9: If 6 is not a factor of d, is 12d divisible by 6?

MGMAT's answer and explanation: The fact that d is not divisible by 6 is irrelevant in this case. Since 12 is divisible by 6, 12d is also divisible by 6.

My concern: I think the answer is incorrect since it has been mentioned on top that variables are integers so if d is 0, then 12d becomes 0 hence it's not divisible by 6. Any feedback regarding this question is appreciated.

Kashif Sear.
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by Rahul@gurome » Mon Nov 15, 2010 10:12 pm
ksear wrote:...
My concern: I think the answer is incorrect since it has been mentioned on top that variables are integers so if d is 0, then 12d becomes 0 hence it's not divisible by 6...
Every integer except zero itself is a divisor of zero.
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by ksear » Mon Nov 15, 2010 10:18 pm
so in other words, every number is a divisor of 0 (except o itself), be it 2, 100, 225 etc. ?

Pls confirm and thanks.

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by Rahul@gurome » Mon Nov 15, 2010 10:28 pm
ksear wrote:so in other words, every number is a divisor of 0 (except o itself), be it 2, 100, 225 etc. ?
To be precise, every integer is divisor of zero (except zero itself), be it 2, 100, 225 etc.
The reasons I'm not saying "every number" are,
  • (1) In general divisibility is defined for integers only.
    (2) 'Number' is a vague term in mathematics.
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by ksear » Mon Nov 15, 2010 10:30 pm
Yup I understand. Thanks.