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For a,b,d are the positive integers, and d|a means that “a is divisibl

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For a,b,d are the positive integers, and d|a means that “a is divisibl [#permalink] New post   11 Feb 2016, 23:02
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For a,b,d are the positive integers, and d|a means that “a is divisible by d”, if d|ab, which of the following must be true?

A. d|a
B. d|b
C. d|2ab
D. d|(a+b)
E. d|(a-b)


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C
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl [#permalink] New post   12 Feb 2016, 00:56
d/a means a is divisible by d

d/ab means ab divisible by d.

all are integers so ,

if ab is divisible by d,

1 a can be divisible by d
or
2 b can be divisble by d.

so the question stem asks must true.

so option a and b are could but not must.

option c is 2ab divisible by d. if ab is divisible by d then 2ab is divisible by d.
option d and e we can't predict.


so option C is correct.
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl [#permalink] New post   13 Feb 2016, 22:38
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For a,b,d are the positive integers, and d|a means that “a is divisible by d”, if d|ab, which of the following must be true?

A. d|a
B. d|b
C. d|2ab
D. d|(a+b)
E. d|(a-b)


--> d|ab is ab=dk(k=integer) and also 2ab=2dk can be divided by d.
Therefore, the answer is C.
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl [#permalink] New post   04 Mar 2016, 17:26
HI MathRevolution,

MathRevolution wrote:
For a,b,d are the positive integers, and d|a means that “a is divisible by d”, if d|ab, which of the following must be true?

A. d|a
B. d|b
C. d|2ab
D. d|(a+b)
E. d|(a-b)


--> d|ab is ab=dk(k=integer) and also 2ab=2dk can be divided by d.
Therefore, the answer is C.


d/ab = k => dk = ab. I dont know how could you give conclusion that ab= dk?
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl [#permalink] New post   07 Mar 2016, 16:34
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oanhnguyen1116 wrote:
HI MathRevolution,

MathRevolution wrote:
For a,b,d are the positive integers, and d|a means that “a is divisible by d”, if d|ab, which of the following must be true?

A. d|a
B. d|b
C. d|2ab
D. d|(a+b)
E. d|(a-b)


--> d|ab is ab=dk(k=integer) and also 2ab=2dk can be divided by d.
Therefore, the answer is C.


d/ab = k => dk = ab. I dont know how could you give conclusion that ab= dk?



-> Because ab is divisible by d.
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl [#permalink] New post   08 Mar 2016, 00:26
Thank you MathRevolution :)
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Re: For a,b,d are the positive integers, and d|a means that “a is divisibl [#permalink] New post   14 Mar 2016, 05:55
Nice question..
Here as AB/D = integer hence 2AB/D = integer
Hence C
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Re: For a,b,d are the positive integers, and d|a means that a is divisibl [#permalink] New post   20 Apr 2022, 09:17
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Re: For a,b,d are the positive integers, and d|a means that a is divisibl [#permalink]
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